While I'm not terribly proud to admit it, I actually own a Crate BX2115 1x15 combo amp. I've recently joined up with a blues/jazz/classic rock band, and it's held up well at rehearsal, but I'm not sure if I'd need something more for playing out. I really know very, very little about amplification. My questions are as follows: 1) The amp is rated 220w @ 4 ohms / 160w @ 8 ohms "minimum load," so if I would add another cab (probably a 4x10) to it, would I need a 4 ohm or 8 ohm? 2) The back panel of my amp has a PWR Amp IN 1/4" jack, so if I were to buy a head at some point, would I be able to plug it in there and bypass what's in the combo amp, now? 3) If I'm completely off on the PWR Amp IN thing, could I just unhook the speaker out jack from the combo's head, and put it into a new head? I figure with the combo, I'd be alright in small venues... with the combo and another cab, I'd be okay volume-wise in larger ones... and with a new head, I could get a better tone out of the deal... and eventually phase out the combo amp, altogether. Does this make any kind of sense?