Is nVidia Geforce GT640 good graphics card for PrE10 despite low memory bandwidth?

Question

Can anybody confirm that the nVidia Geforce GT640 is a reasonable graphics card for Premiere Elements 10 and Photoshop Elements 10?
The person who assembled my Core i7 3770K desktop with 16Gb of RAM at 1600mHz installed the nVidia GT640 card with 2Gb of DDR3 memory. He said that this was a good (fairly low cost) card for video editing because it has 384 CUDA cores - very helpful in video editing. I am pretty ignorant about graphics cards, but like the low power usage, 65 watts, and reputed cool operating temperatures. I have since read that DDR5 memory would have been much faster because of greater memory bandwidth - say 80-90Gb per second compared with 28.5Gb per second for the DDR3 memory on the GT640 card. I was after economical power use. DDR5 cards use 110 watts upwards and run much hotter than DDR 3 cards, all other things being equal. The really fast cards require special power units and cooling.
Does anybody know whether limited memory bandwidth is important in video editing? Is speed much more critical in gaming than in video editing? Are other attributes such as 384 CUDA cores, nvenc syncing, dedicated encodment, 28nm Kepler architecture, 2Gb memory frame buffer, 1.3 billion transistors, plenty of texture units -  more important than memory bandwidth in video editing? Does bandwidth limited by DDR3 memory affect quality of image?
I read that the GT640 would be much faster (producing better image quality?) than the HD4000 integrated Intel graphics of the Core i7 Ivy Bridge processor. Is this so?
Windows 7 Home Premium 64 bit and all programs are installed on a 120Gb OCZ Agility 3 solid state drive. My data drive is a 1Tb Seagate SATA 3 at 7200 RPM. I have a beautiful 21 inch ASUS vs228n LED monitor and LG blu-ray burner.
I did lots of editing with PrE 3 with a Dell 3.06 gHz hyperthreading desktop and Win XP. The output and even the preview monitoring was clear and stable. I am still capturing standard definition mini dv tape by firewire from a 3MOS Panasonic handycam, but plan to upgrade to HD 3MOS with flash memory. I make the preview monitor really small - about 7cm wide - in PR10, because the quality of the preview picture is much poorer than the quality that I experienced with the Premiere Elements 3 program with Win XP. Is this just an indication of memory-saving in PrE 10 previews? I expect output to be much superior, although still mpeg2-DVD quality until I upgrade my camera. I have set rendering on maximum bitrate.
Anyway, despite these reservations with preview quality, the GT640 seems to be performing fine. Picture quality in Photoshop, online and elsewhere on my computer is excellent.
I updated the nVidia display driver only yesterday to version 306.23.
Nearly all graphics cards forums are about gaming. I hope to see more forums about graphics in editing here.
What do you think of the 2Gb nVidia GT640 for editing with PrE 10 and Photoshop Elements 10? What would you say about picture quality in the PrE 10 monitor versus quality of output? Was picture quality in the PrE 3 monitor sharper and more stable, as I imagine?
Regards, Phil

Answer 1

Sheltie,
Thank you for the kind words. We all work very hard to help others with video-editing. Some of us also show up on other Adobe forums, depending on the products that we use most often.
Besides helping out, I also find that I learn something new every day, even about programs that I have used for decades. Heck, I just learned something new about PrE vs PrPro (my main NLE program), when I went to try and help a user. I probably actually use PrE more to test my theories, or to replicate a user's problem, than I do to actually edit my videos. Still, when applicable, I do real work in the program.
With about a dozen "regulars" here, if one of us is not around, several more usually are. Personally, I do not understand how Steve Grisetti and John T. can dedicate so very much time here. Steve is a noted author of books on PrE, PSE, Sony DVD Architect, and others, plus helps run a video/photography Web site, Muvipix.com, that is very active, and has so very much to offer. John T. is always under the watchful eye of The JobJarQueen, and gets dragged, kicking and screaming, out into the yard, or up on his roof, so can be gone for a bit.
Neale usually beats us all, since he's in the UK, and normally answers all the questions, that come in too late for us to see. He is also a PrE power-user, so beats me hands down.
I travel a great deal, but no one ever misses me. Was supposed to do a trip to Sydney last Dec., but had to cancel. Have not gotten details on the reschedule of that trip, but it would have been my first jaunt south of the Equator. Gotta' make that happen.
Good luck, and happy editing,
Hunt