GT 240 512 ddr5 or 1024 ddr3

I'd get this instead since your going off rebate anyway..

Little cheaper. Oh and DDR5 512mb, you'll never use 1GB of memory on that card.
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

This is a good card in that price range too... (Just to give you something to look at)
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Hm. Thanks for the suggestions. And I had been leaning over towards the 512 ddr5 side after looking at these benchmarks http://www.tomshardware.com/reviews/geforce-gt-240,2475-11.html, seeing as the 512 ddr5 is about the same as the 1024 ddr5 throughout the tests i looked at. But those are higher end versions of these cards I'm assuming.

Oh yeah! I forgot to mention my main limiting factor. My computer only has a 300w power supply. That really cuts down my choices.

As helltech said above, get that HD5670, you won't need to upgrade PSU, your current 300W PSU is just enough...  

All I'm seeing on 5670s is 400W, and they are mostly a little too expensive.

at load the ATI 5670 won't break 250w, see link below, so you will be fine with your current PSU. Plenty of people run the ATI 5670 on a 300w PSU.

http://www.techspot.com/review/240-ati-radeon-hd-5670/p...

the ATI 5670 is actually cheaper out the door then the GT 240's you linked. Both have rebates (the Nvidia's is better) but you will have to wait 6-8 weeks to receive it assuming you filled it out correctly and their are no issues on the rebate center's back end.