I'm currently running the o2 air pro m2.5k and I am beyond satisfied. I bought from a friend who was in need of the cash and after looking for reviews to no avail, Im glad I took a chance on it! I have yet to get subs that are worthy of its capabilities, but the closest I've had it on yet is 2 Sundown SA-12s in custom tuned box for them. It slams, I had it doing 2200Wrms and that was at factory voltage before I installed second battery. very accurate voltage/temp display, very clean power, and did I mention virtually no dimming? Very efficient, not very well known, but if you ask me, worth every bit of $325 or more. I've had much more expensive amps that didn't perform as clean and efficiently even with more voltage! I usually go with the names I know well from childhood, but this amp is a beast, and I'm glad I took a chance on it