Check out the 990 manual - there's a pretty good walk-through on how to use an SPL meter to calibrate a system that can apply to the 990 or any other surround receiver or processor. Yo might point your friend in that direction if he has found the meter to be intimidating. It's not really a problem at all once you have some good instructions in hand.

If space and budget permit, the LFM-1 Plus and LFM-2 combo should certainly prevent any future "bass remorse" in your 1800 cubic foot space. You could run the Plus with the port plug in to get the bottom end, and the LFM-2 would help it cover the bass in the 30Hz and up territory with plenty of oomph while still letting it integrate nicely with the full range speakers. Connecting them wouldn't be hard: just connect each to one of the subwoofer outputs on the 990 (it has two sub outputs right next to the unbalanced center channel pre-amp output).