I've been a long time audio enthusiast in both HT and 2 ch. Just to preface my current stereo setup to give you an idea of what I'm running to help make me a recommendation. I'm currently running a pair of Revel Gem's using a tube preamp. Measured response is pretty darn flat in room with a slight tapering off at ~18khz. I really dig a warm sounding speaker with deep tight bass. I've been using electrostats for a long time before settling on the Revel's.
I currently use a pair of RE-0's at work and they're adequate but I'm looking for a full sized solution at my home desk. I have a Topping TP 30 I use to power some small speakers and was planning to use that as a headphone amplifier as well. Probably looking in the area of 200-300$ new or used for a pair of cans.