I can't point you in a cheap direction on this... It all depends on your budget.
I suggest the following cases for modding:
Antec SX-830
Antec SX-1030
In-Win Q500
Enlight 7372
Addtronics Cases
AOpen HX08
These are all the best in my opinion, I currently have a modded SX-830 and it fits me perfect, I got it from EMS Computing for $93 shipped. This case is pretty heavy, but is also very well made and sturdy. I also have an Enlight, this case is very cheap, lighter than the Antec, and has a lot of cooling potential if moded. These two cases are mid towers, if you're looking for a full tower you should go with In-win or Addtronics, they're both very nice cases, however the Addtronics is a bit more, but still great quality.
All of these cases right here you'd have to mod on your own if you wanted high quality cooling. HOWEVER... if you do have a bit of money to spare, head over to Caseetc.com and they sell pre modded Addtronics and other good quality cases, a bit pricey though. =\