Every recommendation here is very good...
At $150.00 you can't beat the Musiland Monitor 02US, it also will do all sample rates 16/44, 24/48 through 24/192 through all inputs spdif, toslink and even USB, it is surprisingly musical.
The HRT sounds very good also, but is USB only and samples up to 24/96, but the easiest to use of the bunch as it is powered off of the usb. I have not heard the Hegel, but has a great reputation. The Schiit starts shipping in a couple of weeks, of course no one know how good it will be, but my buck would gamble that it will be excellent. Both these boys have a great reputation and have built some great gear.