Upgrading HP desktop e9260f

[folkrav]

I hate prebuilt computers. Really. But I was out of this hardware-big-game for way too long now (last time I opened up a PC other than for the regular cleanup was back when a powerful PC was running on a P4 with 2gb ram). Now I have a HP e9260f, featuring a i5-750, 8GB RAM and a Nvidia GT 230 (wtf). Thinking about upgrading my GPU to something a bit better, at least to be able to play the latest games smoother... (just tried playing Crysis 2 last week, could only have playable rates at the lowest graphic settings).

Thing is my PSU only drives 350W. After a bit of digging (tried to do my homework before anything else), I was thinking about getting a Corsair CX500 or 600 and upgrading to something like GTX 560 Ti. Got something to offer that would be better than this? Or something cheaper than 560 that would be better bang-for-the-buck? Thanks in advance!

[folkrav]

Other option I see would be to start building some kind of "frankenbuild" with some parts of the HP (something implying keeping the RAM, CPU, BR-writer and HDDs), changing the mobo for something to be able to SLI two cards, but I doubt about the feasability.

Sorry if this sounds noobish, I kind of are. I really am retarded over this, even back then I wasn't that serious about it, and I now have a lot to learn again to be able to catch up on what I missed out all these years in the hardware stuff.

PS: Sorry for the double post. Forgot to edit the first one.