I found one of these 200watt all tube combos at my local music shop, can anyone tell me anything about them, as I can't find any info anyhere? Are they good, it seems to be helish loud!? what speaker is in the cab? what size is it 12/10/210?? can I hook up an extra cab to it, and if so, what impedance? can someone also explain how the two gain knobs in the preamp work?