If you're not overclocking, you might like the card I have. The Sapphire VaporX cards are very quiet, but because they are non-reference you cannot tweak the voltage to get those 1GHz+ overclocks. I still was able to get a decent overclock, though.
But it'll fit in your case, and I believe it has a 2 year warranty (maybe 3 year? I forget)... not the best, but pretty average among the different AIB's. Anyway, Visiontek and XFX offer the best warranties, lifetime for Visiontek and double lifetime for XFX. But, I don't know if they have any models that will fit in your case, I don't know if the reference card is longer than 10.5"... it might not be, but I just don't know off the top of my head.
Anyway, the VaporX card is shorter than the reference, is very, very quiet, and comes with a pretty average warranty. I'm just throwing it out there as another option since it may fit your needs. Good luck with whatever you get!
*edit
Card I have:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102872 (it is a 2 year warranty)
As someone else said above, an overclocked 5850 would give you 5870 performance and fit in your case. XFX's warranty covers overclocking I believe, so you could get that, it'll fit and have a great warranty, overclock it and save a few bucks while having no fitment issues and have a great warranty. Just a thought.