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.
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.