Since you don't appear to be in an overly-competitive area, a decent processor should be able to give you a good overall sound.
IMO, you need a system that can handle punchy bass and short high frequency bursts without holes being shot into the audio. Most processors will do this, but some will not, at least without being set more aggressively than it appears you want.
For FM, I prefer a minimum of 5 bands in the compression and limiting stages. In my view, this allows the audio to be cut up into enough bands where the vagaries of each can be controlled without affecting areas that don't need aggressive control. For AM, I usually go with at least 4, depending on conditions.
It's all personal preference though. If you don't want to spend a lot of money, looking for the perfect box, I'd buy a copy of Stereo Tool and run it on a computer with HD audio (192 kHz rate). That will allow you to generate a composite output, right out of the computer, that will drive many exciters directly.
Stereo Tool has enough gadgets, gimmicks and adjustments to get most anyone into very serious trouble. On the other hand, it has a lot of presets that make good starting points. Find one that's close to what you're looking for, then you can (carefully) trim it over time. Save your work as a new preset as you go along. That lets you go back to the last good one, if you overdo something.