VP150 is sealed. M2s have ports (as CatBrat already mentioned).

If I had a VP150 taking up space I would be more tempted to try making a single "M2 in a big cabinet". You could probably use the unmodified VP150 cabinet on one side and make something similarly-sized for the other side.

The M40 (basically an M3 tuned down real low) has remarkably smooth bass... I always wondered how one or two 5-1/2" woofers would work with similar tuning.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8