I don't even worry too much about the low extension of my amps, since I use speaks oriented more toward the whole range than thunderous bass. To me, a speaker that is -3dB at 50Hz is acceptable, and without even trying, I'm getting -1dB at ~20Hz from the amp. Amps definitely have different 'sounds', and there's no way for me to tell you what you want to hear, you just have to audition, listen,, and decide; but Wayne has it right, the speaks are almost always the low and high freek limitation.
Forum posts and answers from azzles like me are not the answer. You got to try stuff, listen, try again, and post back to us. It's called 'experimentation', and that's what's the answer.
Thanx, Wayne,
Poinz