What do you think?

pretty good. Will be able to run newest games at 1920x1080 resolution with pretty good settings. If you want to max out graphics settings, you might need something better.

will GTA 4 work?

Of course it will work. There isn't a game in the world that will not work on this GPU.

would a i5 be good with this

Which one?

2nd Gen Intel® Core™ i5-2380P processor

This one?
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

It would be a very nice match, however, I'd say it's worth paying $20 more and getting an i5-2500k:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

You get much more bang for your buck that way.

Well I should just say that I am looking at a pre-built desktop with those components.

it is here http://www.bestbuy.com/site/iBuyPower---Gamer-Extreme-D...

Oh.. I'd strongly advice against buying prebuilt computer. If you don't want to build it yourself, go to a computer shop and ask them to do it, that way you can choose all the parts. In a shop near me they charge $10 for building a PC. In totally prebuilt computers they tend to put crappy parts without upgrade path.

what do i need to get to build a computer? as in motherboard etc.

Watch this video, it explains what components you will need and how to choose them:
http://www.youtube.com/watch?v=lPIXAtNGGCw

Thank you so much! I can't believe i was going to buy a pre-built computer! Thanks again!!

Best answer selected by Multisupermono.

This topic has been closed by Mousemonkey