G-card for HTPC or guest gaming

[Rocky_Hardware]

I recently upgraded my computer to a much better set up with the latest i5. This required a new mobo and new RAM so that meant I had quite a bit of left over parts. Add that in with other gutted computers gathered dust, I had enough to make a whole 'nother computer minus a graphics card

this secondary computer has:
8gb of RAM (DDR2)
AMD Phenom II x4 3.0ghz
550 watt PS (30 amps on 12v rail)

The PS is old though and doesn't feature any pci-e connectors and only has a 20 pin to go into the 24 pin motherboard. I was going to get some adapters to remedy this if necessary.

The goal:
Use this second computer as a home theater computer or as a gaming computer if a friend comes over.
resolution: 1920x1080
I'm looking at these used cards:
EVGA GTX 550ti
or the AMD 7750

I'm looking at getting them on ebay as it only costs $60 for either one. Including shipping.
I do know that the 7750 uses power from the motherboard and for that I would definately need the 20 pin -> 24 pin adapter. With the 550ti I'll definately need a molex -> 6 pin adapter..

So with that in mind, what do you guys recommend? I'd like this to be able to play current games, it doesn't have to be high settings necessarily but I don't want low settings either. I hope I didn't forget anything. I appreciate any input you may have!

 

[photonboy]

THIS card:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102969

It's $75 after the $10MIR, and should come with a free game. $3 shipping. I severely dislike e-bay, and unless it's new offering the game deal as well just get it at Newegg.

I recommend you redeem the DIRT 3 code as it's the best game for this card (others too demanding).