Having tried the Quad 306 without the 34 preamp, fed directly by the Naim DAC-V1, I can only agree with what's been said about the 34 pre-amp! Unshackled from the 34, the 306 is a big-hearted little thing, with noticeably deep bass. It soon becomes clear that bass control isn't exactly one of its fortes, since it's all a bit woolly and indistinct (compared to the Hegel H160), but it's certainly enjoyable and a true second-hand bargain at typically less than £200. I'll stick with the Hegel, though, since it has musical dexterity that the little Quad simply cannot match, and that matters to me.
I do wish more audio components were as neat and compact as the Quad 306.