so i know the old 'can i play bass through my guitar amp' question has been done. this is not that question. if this question has been answered before in detail i couldn't find it. i have a vox valvetronix ADVT-15XL. 12ax7 tube preamp, solid power amp, 15W amp, 10" speaker, closed back. It's a really nice small guitar amp, surprisingly loud too. I have been using it for quiet bass practice, and it sounds OK, but when i run the line out to my mixer, and hear the amplifier's tone w/o the speaker, it's really really nice. super punchy, nice and tubey. so i was wondering about the speaker. I know that if you run your bass through the guitar amp, supposedly the only spot that you can seriously damage is the speaker itself. So, could i put in a 10" full range/bass speaker and have a sweet combo amp that works about as well for either instrument? will a new speaker sound way worse for guitar? what sort of wattage would i want to shoot for for the speaker [it's a 15-watt amp]? i guess the enclosure size might not be optimized for bass, but has anyone else tried this? is it worthwhile, or a waste of time and money?