I also have the older 2x10. I don't find it lacks for lows at all. Most of the hype around 12's is that you can get more lows and articulation. The best of 15's and 10's. I agree with that, but it doesn't take away from the fact that 10's still sound great. Also, the M-Pulse is a very clean, high headroom kind of amp, 10's are a great compliment to that sound. If you had a Big Block or even a Carbine I could see the need for 12's, but the M-Pulse doesn't really call for 12's.