Has anyone run two amps at the same off a VTL 2.5

I have a VTL 2.5 pre amp.I use it with a VTL ST-150 and a Yamaha M-80.I have different speakers hooked up to each of the power amps.I usually power the system down to switch over the cables from one amp to the next,but there are two sets of outputs on the pre amp and I am wondering if it would do harm to drive both amps at the same time.This would be nice for multi room operation,or just a wider soundstage.Not to mention the pain in the ass factor of switching everything all the time.My main concern would be if I were using the Yamaha while the VTL tube amp was powered down would it harm the amp to have the pre amp sending an input signal all the time.Hope this makes sense.....Thanks.