Get another 12" cab, though their not cheap, but it does make a noticeable difference. I ran one cab at 4 and 8 ohms and it punched pretty well. Added a 2nd cab switched them both to 8 ohms and it sounds great.
Fender Jazz, Rickenbacker 4003
Hartke LH500,Two Hartke Hydrives HX112
Ibanez M35, Hartke Club member #155
Grumpy Old Farts member # 7