70 degrees for an 8800GTS at idle is not normal unless cooling is extreamly bad, like no fans and super clogged with dust...
But all the same 70c is nothing to worry about.
, the cards are more than designed to handle above and beyond this temperature.
. But saying that the 2900s will run up to 110 before they shut down afaik.
. All GTX on stock air will idle at around 70 in normal circumstances. If you had the side of the case and some big ass fan pointing at it then you may see an idle temp of around 60c but the fact of the matter is the GTX's Idle high, always have done. Its not really the idle temperature you need to worry about anyway its the load. As said mine goes up to around 80c which is perfectly acceptable. You worry way to much Will.

my 2900pro is idling around 60 and running at XT speeds on load sits at a nice 83degrees!