I've been debating on whether or not to build this one, myself.

I'd use a big single, since that will simply the canister installation. The ZDZ 80 Super looks promising; but I'm a newbie at gassers, so seek other opinions...

If you'll be getting into the upper classes of IMAC, you still want the same excess power that the flip-flop (3D) guys crave; those vertical upline snaps take some grunt to power through.

There's a couple of old build threads on this model archived here; you can dig 'em out with the search function.