headphone amp under $350

I need recommendations for a headphone amp. I'd like to max the price at $350. I will likely use it with a Sennheiser HD-580. I listen to classical and jazz. I'm going to be using the headphones at night so I don't disturb (and am not disturbed by) my neighbors.

I'll be plugging my arcam alpha 9 cdp directly into the headphone amp. I want detail without the sound becoming analytical and prefer balanced sound top to bottom rather than something that really features the midrange (or lows/highs).

Thanks.