I'd avoid 15" tops unless they're running a 1.4" or 2" exit compression driver. The reason being that 15" cones are often quite rough into the midrange, and even the ones that sound okay have very narrow dispersion - they might sound fine directly in front, but take two steps to the side and there's a big suckout in the midrange. The result is bad sound for most of the audience.
The larger compression drivers can run further down into the midrange, so the 15" covers lower midrange and bass, where they generally sound fine and have useful dispersion.
In your position, I'd look at 10" tops and 15" subs, or maybe one of the bigger RCF Evox systems. I'd seriously consider a mono setup instead of stereo. It's half the boxes to move, and you'll get a step up in quality by throwing your budget at just one speaker setup.
Let us know your budget and any other pertinent info, and we'll probably make some recommendations.
Chris