In the price range you give you should audition a Linn Kolector preamp and LK 140 power amp. I personally haven't found anything better for the money (especially if you use the Linn Silver interconnects). The two pieces can easily be had for $1300 on the used market ($450 and $850, respectively). If you have a Linn shop in your area, check the combination out with your current source and speakers and see how they fit.
If you use a turntable, you will ultimately want a better phonostage than that in the Kolector, but it is perfectly serviceable as a place to start. As for the line stage, I've had to go upwards of 3 K to find one that starts to embarrass it in an A/B comparison. It also has quite a good headphone out, if that is important to you.
P.S. Where do you live? If you have good shops in the area, listen to everything they have. That is actually the best advice I can give.