I was curious about the same thing. I was looking at the Eminence Big Ben. Seemed like a good speaker with good reviews at the right price.http://reviews.harmony-central.com/revi ... g+Ben/10/1http://www.guitarcenter.com/Eminence-Re ... e=4AGGWXX2
I then called Eminence to talk to someone about my planned upgrade, and I spoke to a very nice lady on the phone. I gave her the serial number of my existing Peavey Blue Marvel 15" and she put me on hold to look it up. When she came back, she told me not to bother with the upgrade, because the Peavey Blue Marvel 15" and the Big Ben are the SAME SPEAKER, just with different badging.
I was pretty amazed, but in the process, Eminence earned a loyal customer. I didn't buy the Big Ben, but I've bought lots of other speakers from them since.
If you're not happy with the 15" that's in there, what are you wanting it to do? Maybe you just don't like 15" inch speakers?