I've been experimenting with using [DEL]bi-[/DEL] two amps. My main bass rig is a 250W HK (using a VT for preamp), but for the occasional fuller EQ I've been running a signal (controlled with a volume pedal) into an old 15W Fender Pro Junior. (That's a guitar amp for those unfamiliar.)
Unfortunately I do not have anything like a crossover pedal to send only high freqs to the guitar amp. However, what I tried the other day was to put a NYC Big Muff in between the bass and the Pro Jr. -- my thinking being that since the NYCBM cuts so much in the way of lows, my signal wouldn't be damaging the amp. I rehearsed like this (albeit at lower than performance volume) and really enjoyed the sound I was getting. Didn't even need to turn the Pro Jr up past 2 (w/ the BM set for unity gain)! Something about having that little guy up on top of the 4x10 (near ear height?) really cut through, probably not least because my guitarist has a very mid-centric tone.
I just wanted to put this anecdote out there to get a little feedback on it. Am I still risking damage to the Pro Jr, even with the BM cutting lows? Would possible damage only occur at performance volume? I'm speaking from a position of ignorance here, but that's where experimentation tends to begin, no?