I bought a Belles Aria integrated after following several discussions on the Steve Hoffman Forum and could not be more pleased with the sound quality. Matched with Harbeth speakers, the Aria sounds more realistic than my previous integrated amplifiers, which include Naim XS and SN2 (too brash) and Hegel H90 and H190 (too dark and fuzzy).
Not so much a criticism as an observation, the Aria does benefit from vibration isolation. Placing equipment vibration protectors (EVP from A/V RoomService) under the amplifier really opened up the sound and seemed to make the speakers disappear. I also added a HRS (Harmonic Resolutions Systems) damping plate to the top of the Aria, which really improved the bass response/PRAT. Together, these tweaks made quite a difference and are highly recommended.
I have no experience with the Rogue Sphinx but either product should be a good choice.