Ah, crap - was all excited to get everything all set up and working, and when I plugged in the power and flipped the switch - nothing. I disconnected everything and poked around with the multimeter. In my haste to case the thing up, I shorted my mosfets to ground. I guess I didn't seat my shoulder washer correctly (I mounted my mosfets the same way TomB did in his PCB build), and the metal tab on the mosfet (drain) must be touching the screw, which is in turn touching the case/ground. Are my mosfets fried, or can I just fix up the short and have everything work magically?
EDIT: did some more exploring regarding my mosfets.
I switched around the nut and the screw head (i.e. screwing UP from the inside) and covered the screw threads with teflon tape, ensuring that it would not cause a short to ground, and that the shoulder washer was in place. upon flipping the power switch, a huge spark emits from somewhere on the back panel. needless to say I didn't want to find out exactly where this spark was coming from.
I unmounted the mosfets and let them hang in midair, and turned on the amp for a few seconds - it appears to work fine, the LEDs light up, the mosfets get hot, and no spark. this ensures that I did not knock another part out of place and cause another short.
So this means that there is a problem with the way I've mounted the mosfets. However, I'm not sure what part of the setup is causing a short. I'm going to leave this alone tonight and hope that I can find 4-40 plastic screws at work tomorrow. in the meantime, does anyone have any ideas?
Thanks for your help!