I'm upgrading my old graphics card, you can see my old thread here:http://www.tomshardware.com/forum/330280-33-upgrade-980...
I've narrowed it down to a GTX 470 or a HD 6870.
I have a 450W PSU in storage, currently using a 250W with a 9800GT.
I have a preference for Nvidia cards, but i've heard the GTX 470 has heat crashing problems.
Any suggestions as to which one to pick and what manufacturer? (please keep the price below or around USD $200.)
The GTX 470 beats the HD 6870 i would go for it with eyes closed if it's in a good condition.
There's no GTX 470 new at stores. and if there's it won't be that $200.
you can go for a GTX 560Ti it performs better than the GTX 470 and HD 6870 and for $200 after rebate http://www.newegg.com/Product/Product.aspx?Item=N82E168...
if your PSU is not a quality branded one it will cause serious problems to your PC when you install it, so make sure to have a quality branded 500W PSU to cope with it.
2) The GTX470 is an older technology, and needs a bit more power, like 38a on a 550w psu. If your psu has 38a and is a quality unit, you might try it, but be prepared to change out the psu.
3) The GTX560ti has similar performance to the GTX470 , and needs 500w with 30a on the 12v rails plus two 6-pin PCI-E power leads.
4) For nvidia cards, I like EVGA; they seem to have good support.
5) Your 450w psu might work, and is worth a try. Graphics card vendors tend to suggest stronger than necessary psu's to account for poor quality units and to forestall returns because of marginal power. But you should be prepared to spend an extra $50-$70 for a quality psu.