Stereophile had a review of the Boulder 866 and liked it. The reviewer then compared it to the Krell K-300i he had recently reviewed. You should have look at the reviewer's opinion.
I owned the k-300i it sounds great but does not have a fancy GUI. My fancy GUI is ROON and the KRELL is ROON READY, the highest level of ROON integration. You can even adjust the volume on the KRELL with the GUI (tablet, computer, phone, etc) The volume dial is done on the KRELL and not on software of ROON.