Yeah, I'm pretty sure thats true as well
In EVGA numbers, the last two digits refer to the region (e.g. A for US, E for EU) and then 'R' for standalone card or a number based upon the packaged software.
E.g for the 512 GTS I believe AR or ER is the plain card, A1 is with Quake wars and A3, with crysis.
The SSC GTS 640 was, I'm pretty sure, a G80 with more stream processors than normal, but still inferior to the GT or of course the GTS 512.
Disclaimer: Do not buy EVGA if you are european!