why did you want a low profile card?
HD5670 is not a heavy (hot) card, it's a very efficient card and your dell PSU will handle that card easily, since the card doesn't required additional 6pin power connector from PSU.
ive got a dell gx745 small form factor pc thats why id need a low profile if i want to shut my case. but im not bothered about it being open as it currently is.
yea my gt220 low profile is practically touching my heatsink shroud so i couldnt get a card any longer than that one. ill have a look round ill probly get the 5670 at the start of next month if the dimensions are right,