I have an Ampeg 210 SP combo, the thing is: While I was buying it at Guitar Center, I asked the dude "Can I add an extension cab to this, later?". And he said YES. But it turns out, you can't Can I some how mod it to add a extension cab? Also, could I pre-amp the combo with a 50 watt Traynor head? I don't know why I'd want to do this, for a certain sound I guess.