External monitor for home studio help needed

So I have some recording equipment. In specific I'm running an mbox 2 pro on one of the newer macbooks (160gb hard drive, 2.4 ghz processor, 2 gb of ram).
Also with this I bought a Peavey KB 5 keyboard amp and planned to use it as an external speaker. Should've checked that out first. A keyboard amplifier does not wok as an external monitor. Well it does, but I get lots of feeedback and I'm not sure if that's too good for the mbox. So now I'm stuck with this amp. Is there anyway I can use it as a quality external monitor or should I just try to sell it? I was reading something about power amplifiers, though I'm quite positive that's not what the KB 5 is.

Keyboards amp purpose is to ... amplify a keyboard (with specific frequency response, sound and features made to accommodate keyboards) ! Even if it could work, you'll likely have a sound very far from what even a basic active studio monitor loudspeaker could give you. If you have no use of this keyboard amp beside trying to turn it into a cheap monitor, just sell it and grab a pair of true studio monitors.