Newegg.com - COOLER MASTER Centurion 590 RC-590-KKN1-GP Black SECC / ABS ATX Mid Tower Computer Case - Computer Cases
Includes 2 fans. Has bottom mount for PSU.
Lots of room and decent wire management.
Around $80 shipping included. So it's $10 cheaper than the Lian Li.
Both 120mm though.
The Lian Li that b1gapl suggested is probably a better choice for airflow/pressure.
And the Centurion does have side fan mounts... Blech.
Also
The Antec Two Hundred is a cheap deal and fits your description, except it has one side fan mount.
http://www.newegg.com/Product/Product.aspx?Item=N82E16811129070
Totals about $50 with shipping included
Has a rear 120mm and a top 140mm fan.
Can fit a GTX 275 so I'm sure it can fit a 5850.
Though one reviewer said he had to take a back bay off to fit his 5850?
Another reviewer didn't mention that and is running a 5850 in his.
If you want something that fits your description to a 'T' You'll probably have to go with what b1gapl picked out and I'm certain it can fit a 5850, though I'll check for sure.
I've checked it out, and the Lancool K58 can definitely fit a 5850.
It fits a 5770 (8.2" ~) With what looks like almost 3 inches to spare.
So you should be abled to fit a 5850, no problems in the Lancool K58.
And it fits a 10.5" 9800 GTX+ no problems according to this review.
http://www.pureoverclock.com/review.php?id=785&page=5