Hi, I was wondering if it was possible to use a power amp with speakers as monitor speakers for recording with a computer? Also, would it be possible to use a power amp as a bass amplifier?
You could probably do this, but would you really want to? A powered studio monitor is designed to color the sound as little as possible. The amp is closely matched to the speakers and the cabinet design. Most monitors have more than one speaker, and usually have a separate amp for each speaker, rather than a crossover.

As time goes on, and I've used more different kinds of monitors, I've really begun to notice a lot of subtle things that make pretty big differences in what you hear from the monitors. For instance, I like to keep my monitors on the riser at the back of my workstation. This keeps them at ear level. At one point I noticed that the songs I was mixing sounded thinner and with less bottom end in my car then they did in my studio. It wasn't the car sound system, because other CD's had plenty of bottom end. I realized that my monitors were sending a lot of bass into my workstation, and turning the workstation into a low frequency emitter. I put a few pieces of Auralex under the monitors, and that fixed the problem.

I can't say that it's not possible because I've never tried it, but it just seems like it would be tough to get a power amp to match up with any passive speaker cab as well as a decent powered monitor.