Another "which cpu is better for gaming" question.

That Phenom is terrible due to the really low clock speed, the Athlon II will perform much better in 90% of games, but dual cores are really starting to show their limits in some of the newer games that use more cores. Why are these processors your only choices? I'd say they're both a bottleneck for the 5830.

Budget   I'm not doing a build just looking for cheap manufactured systems to upgrade.

I'd agree with loneninja, of the two the Athlon II X2 would be my choice. However, three cores is about the sweet spot for gaming at the moment. Four cores will guarantee you that little bit more for the future. You can pick up an Athlon II X3 for just a little bit more than the X2 so if possible I'd opt for that. Hope this helps!

i'd say go phenom 9100e and do a reasonable overclock

toms actually overclocked one to 2.4  

http://www.tomshardware.com/reviews/amd-phenom-x4,1935-...

If it's really all you can afford I'd go with the Athlon II, it's got a higher clock speed and will perform better in most games if not all compared to the Phenom. It'll still handle todays games, just not as well as an X3 or X4 processor of similar clock speed.

How will he do that on a prebuilt system? And the original B2 stepping Phenoms overclocked like junk, even if he could overclock it wouldn't even reach 2.4Ghz.

the phenom 9100e does not overclock well, go with the athlon II.

I have the gpu and power supply in my possession I just don't have a system to put them in. I calculated how much a decent build will cost me and it's much more than just buying a manufactured system. Not to mention more work. So far the least expensive triple core system that isn't SFF is around $400 but I can find an Athlon x2 215 system for around $270.

We're all on a budget of some degree so get what you can afford. Overclocking is always a great option like has been mentioned. If an X2 is what your budget allows then go for that   Best of luck!

I really wanted to put together a system that could handle Mass Effect 2 and Crysis fairly well for $500 or less. I was offered a brand new 5830 and an open box Corsair 550 PSU for $250; I couldn't pass that up. So altogether I'll only be around $20 or so over budget.

I'll be honest and did not expect very kind answers. Y'all proved me wrong. Thanks dudes.

Logisys CS-51WBK Black ATX Tower Case 4X5.25 2X3.5 5X3.5IN W/ 480W Front USB Audio
Take that case 40$
then the cheapest athlon x3 you can find. 70$
2 gig ram 50$
and hdd 50$
You are under 300$ and have a perfect computer.

DO NOT BUY READY TO GO COMPUTERS, THEY SUCK  

Believe me I know the advantages of building your own. Just with what you mentioned along with MB, fans, thermal compound and I'm over $300 with 2GB less RAM and more labor.

Not to mention $100 for an OS.

a motherboard is 70$
fans 7$
thermal compoud 10$

50+50+40+70+70+7+10=297   Do it   Just do it  

Before you buy the computer you should look and see if the motherboard supports the Athlon II X3/X4 processors, than you can upgrade later this year or next if you need a stronger processor.

MCP61S I can upgrade to a triple or quad core later.

Keep in mind that many inexpensive prebuilt systems have very lame power supplies in them. It you put that 58xx in one of them, be prepared to upgrade the PS. Personally, I wouldn't attempt to make a gaming system out of an el-cheapo prebuilt. You are just asking for trouble.

Yeah I decided to just build my own. I actually sold my 5830 and Corsair PSU for more than I paid. I'll be posting my build in the coming weeks and ask for opinions.