I'll second on the Accu-Cutter. I looked seemingly forever and finally bought a POS Lassco, then unloaded it on Fleabay. It was a cheap piece of junk, well it wasn't cheap in cost >$150, but in construction.
The Accu-Cutter we got was this one:
http://www.accucutter.com/Cmate 040.htm
It is very well made, machined aluminum. The only real issue I have with it is the "throat" is of limited height, presumably to keep morons from trying to cut 1/4" steel. However, I am a big boy and it irks me that I can't cut corners on Coroplast because it won't fit in and it comes so close. It could also benefit from some sort of attachment for the die, every time I pick it up the die falls out.
On PVC, Polymetal, aluminum it does a good job though. Heck we even use it on photo paper now and again. We went with the 1" radius.
We purchased directly from the manufacturer and paid a hair over two bills.