The question to ask yourself at this point is are the speakers the weak link in the food chain?

What are you using as amp/amps, pre-amps, etc. I've found the Pi 7's I have change the sound RADICALLY depending on amp/ pre-amp/ crossover arrangement. What you may want is NOT more sawdust and solder. I've got this little 40 watt Luxman that defines bass notes like nothing else I've tried. If I hook up a similar wattage Harmon Kardon amp things go BOOM, BOOM, BOOM, and you really have to work at finding the music. Your more of everything is not likely to be speaker related if you have a nice set of 4 Pi's attached.

Good luck on what ever you try. I noticed your size restrictions. Pi 7's are probably bigger than you want to go.

Grant.