You are not concerned about performance, well that is pretty irrelevant in the choice between the two cards. You will be hard pressed to notice any performance difference. So the choice comes down to the extra 512 MB VRAM and the need for it in relation to the price difference. That is something you have to decide. Nobody can help you with that choice.
Out of these two cards, I'd much prefer the 580 with its dual fans if you care about noise.
Regarding is 2.5GB and GTX 570 "power" being enough, yes, it is plenty for what Adobe CS5 and CS5.5 can utilize from a grapics card.
I don't have any links saved (I use very few pictures) but do be aware that a picture that is "too large" WILL cause problems for PPro... including crashing when you try to export
Video card memory is useful for Photoshop, but anything over 1Gig is not going to do "all that much" for PPro
Photo Scaling for Video http://forums.adobe.com/thread/450798?tstart=0
now that IS useful info. THeres 0 point to drop $500 on something that STILL isn't going to work. I currently have 768mb, I wish there was some way to know what the upper limit is for stills size. I currently use 3500x2350ish sized images and pan and scan in Ppro cs5.
Would be great to know if anyone out there is doing something similar sucessfully with 1.5gb or greater. THere are lots of cheaper cards out there with 1.2 or 1.5GB of ram. (But still no point in me getting one of these if its still going to crash on export)
thanks jim and harm: I meant I'm not interested in the performance of either card. I picked them for the amount of ram they carried.
As I said, no links saved since I use very few pictures
But... I think that in the past week I've read a message about exporting and crashing due to large pictures
Could have been here, or over in http://forums.adobe.com/community/ame or maybe even in http://forums.adobe.com/community/encore/encore_general
Sorry... just of passing interest to me... maybe someone else will have an actual link
That is probably the discussion I remember... especially the comment that the program choked on each large picture, until all pictures were reduced in size
I do not know if you have seen the fact that nVidia is coming out with a new GTX 600 series in the November/December time frame. So if you can work around your problem for 3-4 months there will be a whole new generation to pick from and you can buy yourself a nice Christmas present.
I just ordered a Gigabyte GV-N450 oc2-1gi, just € 92,95 ..$130,- I think.. with 192 cuda's and 1024 mb gddr5 and 2 fans.
So when the 600 series come, I just sell the 450 for € 50,-