What GPU should I buy.

Hi. Would someone please help me with the this problem: I have a AMD Athlon 64 X2 6000+ and 4 GB DDR2 800 MHz and I want to build a PC. The problem is I'm not shore wath GPU to buy. I only had low-end PC configurations ( the best I had is ADM Athlon 64 X2 4000+ 2 GB DDR2 800 MHz and ATI 2600 Pro 512 DDR2 128 bit ) and I had Intel and AMD CPU's and nVidia and ATI GPU's. What GPU should I buy that is adequet for my CPU and memory. Money ... let's say 200-350 bucks. I usualy prefer nVidia but if ATI offers better performance for my bucks then I'll take it.

Tnx in advance for your reply and advice.

And how long will it last ( as performance ) ? I'm only building this PC so I can game until a realy good GPU and CPU comes put, like the next generation of AMD and Intel. Will 8800 GTS 512 last for lest say 9-12 moths ?!?

I would like to think that HD 4870 would be a very good GPU ( gDDR5 sounds sweet ) but a have a bad feling about it. I always have been and will bee a fan of AMD ( only CPU ) but when I meant a next generation a wuz speeking about a very good optimized ( hardware and software ) quad core that a dude like me ( I'm from Romania and in the East part is not so full of money. for example a child pay from the state is 15$ and the avrage salary is about 250-400$ ). I'm waiting for the big fishis to settle down ( Intel's Nehalem abd nVidia's 280 GTX ) for drivers optimization and price cuts. I want to build a dream gaming PC ( about 3000-4500 $ ) so i have to start collecting money so it will take me about 12-16 moths. And by the way a read the GeForce 280 GTX and I think it's have issues but 1GB memory and a large bandswitch is prety good, and if it cane really handle Ageia's phsihics then I would buy it but for now 650 bucks is reeeaaahhhhiiihhhiiiihiiiily to much for me. mkay.

PS. I'm not a AA or uber high resolution ( 1680*1050 is more then enough for me ) and how the F*** is willing to pay 400-600 $ for a LCD with a biger resolution. what is up ith the hole 1920*1200 or the big one 2560*1600. whats up whit that, i even seen people playing at medium seting just to cracnk up the resolution. those people are wankt.