If you underclock it to something like 700 core and 800mem it should run ok in a micro-atx case or mini itx case. Something like a shuttle or micro atx case.
Cooling will be a concern so i doubt it can run at stock speeds in a crammed case.
Have you considered a "oldschool" desktop case? I converted my tower to a desktop.
You need a tower case with 4 dvd drive bays. Flip the drives sideways, tiewrap them in place. Get some black open cell foam (lots of boards are packed in this foam so look in your old boxes) You can also buy filter foam.
Cut it a bit bigger there should be a groove between the plastic front and cage to tuck the sides of foam into so it stays put.
I put my monitor on top of the case that now sits sideways. It saves alot of space. Also the monitor sits at a better height right in front of you.
To do this you need a standard atx tower with 4 dvd rom drive bays.
You can leave the drives sideways, most will work like that, but when you open the drive it can hit your keyboard.
I hate tower cases, a big useless tower case it's clunky and eats up space.
My htpc/gaming system is also set up the same way, with my sony 5.1 reciever sitting on top and a 46" lcdtv.
You might want to consider buying a used hd-4870 since tri-fire is known to rock.
Is this related to the post that you had earlier when you were getting two of the 4870x2 cards and are you putting two cards in this case that you want?
This Silverstone case is on the exspensive side but will fit cards up to 12.2 inches and comes with a 600w power supply.
Yeah it will fit if you pick the right case into a mini-itx or micro-atx case. The 4870-x2 is about the same size as a hd-6970 or 580. It is a single card with two hd-4870's in crossfire.
Adding a regular hd-4870 would give you tri-fire on a crossfire micro-atx board on the cheap, but you would have to underclock them a bit to make it stable. Well anyways 2400 shaders at 700mhz core/800mhz mem is no slouch and would give the new hd-7950 a run for it's money.
That could be crammed into a shuttle like micro-atx box.
Im doing a retro build, I have 2 brand new 4870x2's that are still sealed in the box, I just really dont want a big eye sore case, But from past experiance i know that even in a rv02 one 4870x2 was loud as hell. Need to figure out what case will honestly be best for 2 4870x2's