Either way is the gpu that I have at the moment the best for around $100?
Yes. Today's 5750 performs the same as the 4850 and costs somewhere around $130 normally.if i were to go with nVidia
Don't. And you will find that SLI/crossfire info on either the site you are getting the motherboard from, on the manufacturer's website, or in the motherboard manual.And if I need another one which do you recommend?
For going crossfire/SLI? Both should be the same model, or it could be detrimental to performance.Nothing in particular, i just want a solid computer that will be easy to adapt in the future.
Then wait for bulldozer next year, or get the 1055t right now.