first thing is the software you are using. adobe products are had a good partnership with nvidia for quite some time.
i would suggest to stay away from low end quadro cards. they are only slower clocked geforce cards with better driver support.
if you want gpu assisted rendering then cuda; particularly femi gpus are the way to go, like 480 of them cores:GeForce GTX 570EVGA SuperClocked 012-P3-1573-KR GeForce GTX 570 $279.99
$259.99 after mail-in rebate card EVGA SuperClocked 012-P3-1573-AR GeForce GTX 570 $289.99
$269.99 after mail-in rebate card
there are cheaper 570 cards but EVGA has great customer service and the first card has a 3 year warranty and the second has a lifetime warranty.