I urge everyone who is interested in the HF-81 to try Pilot 602 receiver which has outraging bass and presence, at least on my Tannoy Arden II, MG III LZ, and even the low efficiency (read: 81.5dB/1 watt) Celestion SL700.
These two EL84 PP amps seem to have comparable output transformers and I suppose their sound should be similar. Not the case, to me at least. The Pilot 602 doesn't even sound close to the Fisher SA-16, a console amp from the 50's. The Fisher has thinner bass, though.