I have a question about the Ampeg BA-115. Can you use another speaker cabinet with this amp? I was thinking about getting a 2x10 cab. The reason I ask this is because some combos, such as a Crate, shut down the amp's speaker if an external speaker is added. If a cab can be used with it, is the 100 watt enough to push the 15" plus a 2x10? Thanks.