Not at all suprising you would be dissapointed in bass perfomance with that matchup - I don't think the bass performance you were hearing is an inherent quality of the amp, but of that particular pairing - for that speaker it seems you would need current to really drive and control it, not sure the DA60 would be ideal either, though better. I would get a 100 (or more) SS integrated to drive that speaker (86db, 4ohm and probably quite a bit less than that in the bass region - not ideal for 35 watt tube amps).