Hey, I didn't even think about the pre-outs, entirely possible since it's probably 5 years old at this point. Right now I'm using the sub-out specific plugs, would the front and/or rear outs be affected the same way, if there is a problem?

The sub isn't dead, so the 9-volt trick will show positive. I should see if I can borrow a sub/box from a local store to test my amp, good point!