I used to run a set of bi-amped Event PS 8's ( I think, don't remember now), but they had a scooped mid and didn't translate well. Now, thanks to a friend, I use a 1973 or so Pioneer SA 9100 amp with a set of Yamaha NS-A638 speakers. I've seen the amps on ebay before for a couple hundred or so but haven't seen the speakers. Of course, I haven't been looking any more so......
IMHO, these 2 pair up to make a great monitoring system. The amp has plenty of power and the Yamaha's have a nice overall balance. Again, just my opinion so take it as just a little more food for thought.
Peace...............