First of all don't use an old AVR for power. There are no real benefits and I'm not sure why you think you need more power in the first place. You have Klipsch speakers, which have pretty darn good efficiency. I could run the numbers for you if you really want, but for now I'll just say you're not going to be pushing more than 20ish watts to get them to referenceish levels from about 9 feet away.
You mentioned being unhappy with the single crossover setting, but adding an external amp won't fix this. If that bothers you, then you have to upgrade.
Right now you have speakers that can easily be driven with an AVR, more power really shouldn't be an issue unless these speakers are in a huge room. Better room correction would definitely help, but that would go along with upgrading the AVR as well.
You could always tweak the level adjustments for different speakers if you want it louder as well.