Heh, look at some of the classic Lian Li cases. All aluminum too. They're easy to mod as well as a result. They are however fairly expensive. The case in my sig is actually pretty large. Plenty of room above and below the mobo mounting tray for pretty much any mod you'd ever want to do.
The Cooler Master Stacker 101 I believe which is older is another favorite of the modding community. You can mount a 3x120 rad in front since the entire front portion is made up of mesh grills or even on the bottom if you decide to mount the PSU at the top of the case.
For a mid size, the Cooler Master 690 is great to work with. I actually bought one to mod for my fiance. I posted a picture on the thread for CM 690 owners.