Bass/acoustic amp...

You could go with a PA head and a full range speaker(s). Keeping it under $300 is another story.

But you could do it like this:

Behringer PMH518M Powered Mixer

And...

Kustom KPC15 15" Full Range Speaker

You could start with one speaker. This is 8 ohms, so the 180w amp @ 4 ohms would put out about 70% power at 8 ohms, or 125 watts approx.. This would be pretty powerful, you could play small or possibly medium sized gigs. Plus you get effects for the acoustic guitar (or bass), EQ (very nice), plus channels for mics if you sing. This is how I would do it under your budget.

Pick up another speaker like this and get the full 180 watts at 4 ohms.

PAs like this are solid state which is ideal for bass and electric acoustic guitar where you want clean undistorted tones. If you want distortion, it is included in the effects, or pick up a pedal.

I used to play a club that had these Kustom speakers for sound. They really sounded very good to me, we used to run bass through them all the time.

I read once in a review of the Carvin AG100 (acoustic guitar amp), that it could be used for acoustic guitar, bass, keyboard, and as a mini PA system. Then I was looking at other keyboard amps, bass amps and acoustic guitar amps, and saw some similarities. For one, they all have closed back cabinets, which, like in bass amps, allow a deeper frequency response and don't let the bass driver to move too far and perhaps fail.

The other thing is that they usually have piezo tweeters and maybe a midrange speaker/driver, and more tone shaping controls. They're like powered mini-PA cabs with tone shaping / feedback notch controls designed for acoustic guitars and keys.

In other words, an acoustic guitar combo might be able to handle bass guitar if you don't push it too hard. If you get one that has a tweeter defeat switch, you could disable the tweeter when playing bass, and then enable it when playing acoustic. I have a small Fender bass combo which has a tweeter setup like this. I haven't played my acoustic electric through it, but I know I could adjust it to work at least nominally with it if I had to.

But I also checked out the little Marshall acoustic amp (didn't get it because I'd switched to bass at that time), and besides it having a smaller bass driver and a tweeter, it had the same sort of closed back cabinet as the bass amp, and again, I knew I could put a bass through it (at low stage volumes) in a pinch.

I haven't tried keyboard amps, but if you think about it, playing an electric piano through an amp would be a combination of both bass and acoustic guitar. At least the way I see it. It has to be full range like an acoustic guitar amp (though acoustics may not need the really low frequencies - in fact you might want to dial out the low sounds to prevent that 'woof' type top feedback), but it has to have the lows to put out what a keyboard can put out.

Maybe for low volume bass guitar or regular volume acoustic, you could try an acoustic combo. For higher levels in both, you could try one of the keyboard amps available today.

I still think that a lot of the acoustic guitar amps and smaller bass guitar amps are basically the same amps; just with slight variations in tone shaping.

Just my opinion though.

Thanks for the replies. The speaker system looks worth checking into, but i also like the idea of a keyboard amp. Both make sense! thanks again

For the speakers you put a mixer in there. I was wondering, if I have a Inspire recording interface pre-amp thing, that would work just as well right? Looks like it has outputs for speakers so im assuming it does. Just checking