VC purchasing advice

Hey,

I have a AMD x2 3800 with 1gb ram (pc4200 @533mhz) and a Nvidia 6150 (sucks). It only has a 300w power supply http://www.power-on.com/atx12vhp300bt.html (Link to power supply.) The case is small, so overheating could be a problem for the hotter cards.It also has a PCIx slot available. Now, will i need a new power supply? I'd prefer to avoid purchasing one if it is at all possible.

Now, I am looking to upgrade the video card. I'd prefer to spend under $200, although I might use this card in a new computer that i'll purchase next year, so i am willing so spend an extra couple of $$$ if the performance gain is significant.

Are there any good cards in the $150 range that do not require a lot of power?

Lastly, I saw that people were saying they found the 8800gts 320mb available for $250, but i could not find anything for less than $275.

Thanks

here is a good card http://www.newegg.com/Product/Product.aspx?Item=N82E16814130056

but if ur on a budget here is a good card also http://www.newegg.com/Product/Product.aspx?Item=N82E16814130062

heres a good psu http://www.newegg.com/Product/Product.aspx?Item=N82E16817104954

heres another PSU but the company has just started in business. but it has great reviews :) http://www.newegg.com/Product/Product.aspx?Item=N82E16817189005