enaher :
I would go with the 2600xt its really cheap at newegg and should out perform the 8600gt w/o AA and that version of the 8600gt has only ddr2 vs ddr3 so this should be a better choice http://www.newegg.com/Product/Product.aspx?Item=N82E16814102700
Yeah. I was looking at the HD2600xt as well, but there are a couple of reasons I didn't recommend it.
1. It's Sapphire, and from what I've heard, their customer service is pretty ****.
2. It's only 256mb.
3. The clock speeds aren't shown, so you don't really know what you're getting.
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http://www.newegg.com/Product/Product.aspx?Item=N82E16814145146
also, there's a GDDR3 version of the 8600gt. It's a couple dollars more.
All three cards should perform around the same, with the GDDR3 version of the 8600gt leading the pack somewhat.