I do not know about APUs, but the the best discrete card for R600g is the Radeon HD 6870 based on Phoronix benchmarks as well as my own experience.
http://www.phoronix.com/vr.php?view=20732
http://www.phoronix.com/vr.php?view=20509

When it comes to RadeonSi I can not say, but you should be able to look up some more Phoronix benchmarks and draw your own conclusions.

sorry to jump in but what is the best ram money can buy for a Linux system ?

Quoting: GuestDisclaimer: I run Gentoo, compile my own kernel, and tweak my system a lot. So I might expect different results compared to, say, Ubuntu.
I have a Kaveri running ok with open source drivers. You will get better performance from fglrx, but I've had no stability problems from RadeonSI, and it will run most "light" games just fine. I haven't actually tried the very latest Mesa release yet on it, though I should do that next time I reboot it.
But if you grab just an APU, I recommend two things: get a case large enough to install a discrete video card later (just in case you want to upgrade at some point), and do put in a little extra money for decent RAM. For integrated graphics, fast RAM will definitely make a difference.

Thanks. I'm manjaro user and I hope it will run good.

Current System
Ubuntu 14.04 LTS
AMD A4-5300 APU
Open Source Driver
Resolution 1280 X 1024
RAM G.Skill Ripjaws Series 4GB (2 x 2GB) DDR3-1600
1 TB WD Blue

I need a computer on a extremely tight budget last year $350 apx(tax and shipping). the APU has served me well. I was able to play any 2d game I threw at it. hulu and youtube worked perfectly (huge issue for me on my older computer). however 3d has been a struggle for 2 reasons. 1 not many 3d games for linux i wanted. 2 90% of 3d games involved wine. hit or miss situation.

(Most Games Mid to Low settings)
Linux
Team Fortress 2 - Good
AntiChamber - Great (Max Settings)

Wine
Batman Arkham Origin - Ok windowed (some slow downs)
The Darkness 2 - Good
Dead Space - Good windowed (Some graphical hair issues)
Mini Ninjas - Good
BioShock 1 - Ok windowed (crash-a-thon)
Mount & Blade - Great
Payday 1 - Great
Company of Heroes - Good
KOTOR - Great
Overlord - Great

this is just an example of some of my games and what i can get out of it without using the amd driver. it should be noted that i had some graphical issues because its amd.

I would recommend not gettting my APU. its great for work and light gaming but the day will come when you want to do more. I would suggest to look at A6-A10 models with Richland and up. And like mirv big case for future upgrades.

Quoting: GuestI use DDR3 1600MHz as well, something from Kingston in my case (pun intended), 2x4GB.
Large textures and game resolution will kill performance (particularly with "lesser" RAM), but I still run everything at 1080p (just because).
Definitely go for the later models (I have an A10-7700K). From what I can tell, fewer driver problems with Kaveri as well. Carrizo (successor to Kaveri) is supposed to be out mid-year, and should use socket FM2+ (same as Kaveri), but I'm not sure for APU generations beyond that. Something else to keep in mind.

I have been getting that impression that the amd driver would work best on the newer chips. and whatever bugs pop up with the older APUs wont see a fix. mirv can u handle any of the new AAA game ports ex. Bioshock Infinite with just the apu?

Quoting: GuestJust trying to think of other games....Trine2 was about 30fps at medium settings, but I'm not sure vsync was really disabled when it should have been.

Keep in mind that Trine 2 was designed to be played at 30 FPS.

I am actually surprised that Shadow Warrior did that well for you on an APU.

Both my brother and I have managed to get to Chapter 12 of Shadow Warrior using R600g. Some areas do get bogged down pretty badly even with discrete cards, but others run at close to full framerate sometimes, so there is definitely some bottlenecking going on. This is on both a Radeon HD 6870 (Arch Linux) and a Radeon HD 5750 (Fedora 21) using stock drivers.

I also had a strange graphical corruption on Chapter 5 wherein the screen would start to display only garbage after entering a certain room towards the end of the level. I got around this by cranking my settings down from Ultra to Low quality. The fact that that was the only discernible difference between the two states definitely shows the problem is just it struggling to handle certain always enabled effects.

Quoting: kalinHi.
I want to buy new relatively cheap pc for gaming on linux and anything else.
I want to buy amd video because of vulkan(amd is responsible) and better pollicy of the company.
I also want to ask how amd apu perform with open source drivers. Is there anyone with experience ?

Their policy is to not give a shit about their customers. Yeah, let's support them!
Also, what's the point of open source drivers when they are not delivering the best performance? - Most games are proprietary anyway.

Quoting: BrotAmStiel

Quoting: kalinHi.
I want to buy new relatively cheap pc for gaming on linux and anything else.
I want to buy amd video because of vulkan(amd is responsible) and better pollicy of the company.
I also want to ask how amd apu perform with open source drivers. Is there anyone with experience ?

Their policy is to not give a shit about their customers. Yeah, let's support them!
Also, what's the point of open source drivers when they are not delivering the best performance? - Most games are proprietary anyway.

Well, to be honest, Nvidia doesn't really give a shit either. Remember what happened with GTX 970? Also, a recommendation: do not start an Nvidia vs AMD flamewar, especially on an AMD or Nvidia specific thread. They never end well and usually only get people really riled up for no reason. If you absolutely have to fight with AMD people start your own thread and we can keep it contained better.

Quoting: BrotAmStielAlso, what's the point of open source drivers when they are not delivering the best performance? - Most games are proprietary anyway.

Also, what's the point of open source Linux when it is not delivering the best performance or selection? Most games are proprietary and on Windows anyway.

Maybe it has something to do with the desire to use a computer in the way that you want to?