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Honestly Sean I don't think you are going to get high levels with no distortion, buzzing or humming at only 30 watts. Maybe if you stick to practicing in your bedroom that will be enough power. But the first time you try to play with a guitar player with 50w or a real drummer you won't even hear yourself.

Two things to keep in mind 1)bass takes lots more energy than other instruments. 2)to make bass notes you have to move lots of air.

So 1)more power is better and 2)bigger drivers are better. You can have lots of small speakers instead of one big speaker but the idea is to move lots of air.

Acoustic Bass Guitar

My very first amp was a 40 watt amp. I outgrew that thing before I even had a chance to spill a beer on it. A 30 watter is just going to be throwing money away. You'll be buying something with more power in no time. Headroom is a funny thing. It's better to have it and not need it than need it and not have it.

Dave

I have two bass amps:

Peavey Microbass (link). That's a tiny, highly portable 20watt RMS combo practice amp with 1x8" speaker. The back is closed, so it has a deeper sound than you might expect. It's fine for private practice and for jamming along with acoustic instruments. It can't compete with a drum kit.

They don't make it any more, but they do make the Peavey Max 110 (20watts, 1x10), which is close to the same thing (plus a few modern extras), as well as the Peavey Max 112 (40watts, 1x12), and the Peavey Max 115 (60watts, 1x15).

That Roland Cube you mention is comparable. It's a nice practice amp, and loud enough for something small and acoustic.

Any of those would make a fine first amp. But even the largest of them will have a hard time up against a drum kit. If there are down-tuned, distorted guitars in the mix, forget about it. You'll need 100watts, at a minimum, to cut through. And 200watts is even nicer. For that, I bring out the big guns:

My other amp is a Yorkville 400B, which is almost identical to the BM400, which was a later redesign of it. It's 400watts into 1x15". It can drive an external cab, too. It was around $800 new. They don't make that one anymore either. Yorkville revived the Traynor brand for all its musical instrument amps, including a nice line of bass amps. Their stuff is solid, loud, and built to last. They have amps at every price point. They're made in Canada, which makes them fairly rare in the US (I haven't checked your profile to see where you're from).

I like SWR and GK quite a bit, but I can't recommend a recent model. You'd just have to try 'em out. The WorkingPro line looks good to me, but they're beyond your price range. You might check out the SWR LA series. Those are more affordable, and come in a 10" (35watt), a 12" (60watt), and a 15"(100watt). That top one, the LA15, is $350 and might be a good starter that can keep up with a kit.

Best of luck. Let us know what you end up with.