Yep, I did use a powered PA cabinet for quite a while with a 15" and a hi freq tweeter but I never was happy with the high mid range frequencies. When I got the Traynor with a 12" 2 x 8" and a tweeter I was much more happy about the sound.
Playing in a live rock band with a bass player the hi mids are much more important to me than the lo frequencies. Though if I was in an OMB situation that may be a lot different.
Though the bass player in my band uses a 4X10 cabinet that provides both a great low end as well as crisp highs.