Re: mixer for live sound....suggestions?
Those Yamaha A15 speakers are great by the way. I owned two and they handled quite a bit of power.
I would split the whole thing up, get a mixer, two speakers, and a power amp. I currently use a Mackie 1604VLZ as my console, a Crown 402D power amp (these have been discontinued though) and two Peavey speakers now (12" woofer with a horn), and this set-up works great. I do need a separate effects box, but I'm willing to deal with that due to the routing flexibility of the Mackie. However, my other choice for consoles would be the Yamaha O1v96 if you can afford it.
But, you may be a Mackie ProFX12 type of person if you want some simplicity. The downside to the Yamaha O1v is that you need a sound guy manning it, it's not really a "set-and-forget" board that we so often use with small garage bands, but it can be done.
I understand you're on a budget, but split the components than you can upgrade each one as your needs become greater. I've seen great condition Mackie 1604VLZ's going for as low as $450 on eBay sometimes. Whatever you do, do not skimp on the console. That's the device that's doing most of the work, and if you get cheap components in it (a la Behringer, or Samson), you'll just be dealing with noise and low mic-pre head room, and that's just gonna be another huge headache. I'm assuming you've learned your lessons about buying things like cheap cymbals and drums, the same applies to audio equipment.