I really like trance -- squeaky clean synths, deep tight bass, not a whole lot going on in the midrange -- on my Dynaudio Special 25's, but they're a bit out of your price range, and would need a more powerful amp than you're likely to get for $150-$300. I was told that the Dynaudio in-walls were basically the same speaker without the Esotar² tweeter (well, rather, with a different tweeter) -- the "IP-24", I believe they're called.

As to the preamp-multi power amp setup -- if you use the same amp (or at least the same input impedance on all the amps), there should be nothing wrong with just using a splitter on the output of your pre. As long as its powerful enough. If you're talking more than 4 or so, that might be a different story, but you might just want to get a receiver capable of driving multiple speakers.