Get a better amp. I would caution you against buying a combo amp (amp and speaker all in one package). It is tempting. Looks simple, just plug in and turn it on. When your done, just carry it out.
However, few combo amps really have the volume you will need for actual live performance in a club or at a concert—unless your band is mostly soft acoustic music, Jazz, worship, etc. I strongly recommend that you find a USED speaker cabinet and amplifier (head). This kind of modular approach is actually cheaper in the long run. Look for two 10" speakers (210), one 15" (115), four 10" (410), or two 12" speakers (212). Almost any brand that sounds good when you test it is fine. An amp head that has at least 350 watts into a 4 ohm load is a good place to start.
Almost any brand to start is fine: Acme, Acoustic, Ampeg, BagEnd, Behringer, Bergantino, Eden, Epifani, Fender, Genz Benz, Gallien Krueger, Orange, Peavy, TC Electronics, SWR, etc. Plan on spending around $500 or $600 total USED. Ouch! that's way more than a new $450 combo, why am I recommending you spend 33% more than you need to just get something marginally better than what you have now? Simple. In a very short while, you will likely discover your new amp, no matter what it is
doesn't cut it. Then what?
If you have a combo, you have to save ~$400 all over again before you can sell it
in order to get a bigger/modular rig. You then can sell your combo for say $250—loosing money on it is likely, as your customers are guys like you were looking for a cheap amp. Now your savings + selling your combo = ~$600. Where does that leave you?
Exactly where you are now if you spend $500-$600 for a modular rig. You will have gained access to a slightly better amp, but are still stuck spending $500-$600 to step up, plus you have to sell before you have raised that money.
If you go modular now, when your amp begins to disappoint, you can look around for a better (or additional) USED cabinet, typically about 1/2 the price of a new combo. Keeping your current rig and adding to it instantly gives you more volume for a likely expense of $200-$400. Adding a new head let's you keep your old one as a backup, or sell it to cover most of the cost of the new one after you have purchased the new one.
Same goes for speakers. If you replace a 115 with a 410, you can keep the 115 as a backup, keep it in a rehearsal space, or sell it.
I could go on, but this is already way too long. When you find something you are considering, come back to TB and ask about it. Rinse and repeat, LOL! Good luck!