I've been using a single 12" avatar with an Ampeg 4x8 very successfully because I use a BiAmp head. Because of that I can dictate the frequency split, and the individual volume of each cab. I can set the head to bridged ( Mono) output or split ( BI amp) and the difference is striking. Since I've gone Biamp, I have a small rig that's incredibly efficient , and is very portable and LOUD when I need it be. IMHO. Any single cab alone has shortcomings, but 2 moderate cabs together (i.e your 1x15 + some form of faster motor speaker i.e...10 by?",8 by?",5x?" etc.., Biamp'd, you'll be very pleased. I've owned, Aguilar 2x12's SVT's, multiple brands of 4x8, and 5x6 Phil Jones cabs. 1x15's, 2x10's even 1x10 eden cabs ...you name it. You can get far better sound than you may be aware by splitting the signal and BiAmping. thoughts?