I've heard the pre with the match Onkyo Ref power amp, the system has the Onkyo sound but better than their typical gear. Meaning you get Onkyo's tight bass, extended highs, and I'd say neutral in presentation. Probably not a good match if you like warm or romantic presentation. We compared the built in DAC to the Ref stand alone CDP, I preferred the CDP but any difference was subtle.
The power amp certainly has a retro cool factor and sounds more powerful than it's rating, however, the price gives it some stiff competition. Parasound's Halo for example.
