Hi Troy,
I know you are (probably) not going to want to hear this, but a pair of M100s would certainly give you what you are looking for in terms of an M80v3 with a tad more bass. Since you are going to be sticking with a 2-channel only setup for a while it might also make sense to look into the LFR1100s as they will give you both more bass and a much larger, enveloping soundstage in stereo.
The M80v4HP will be a better all-round performer than the M80v3, but the difference in bottom end is fairly subtle, unless you are really pushing the system where the lower bass distortion will be evident on the HP.
Andrew
