Advice will only go so far before you have to get out there and just try some of the damn things. So many amps, so little time.... I've heard the previous iteration of the Cambridge - it was okay but it wasn't the last word in any respect and at £1500 new they are not exactly giving them away. The QUADs I don't know. My recco would be to go for a pre-power with a passive pre since I reckon that gives a taste of proper high end sound without the high end price tag. Quite a lot of inexpensive options out there. The pre-amp is the most important bit of the amplifier chain IMO.
Current Lash Up:
TEAC VRDS 701T > Sony TAE1000ESD > Krell KSA50S > JM Labs Focal Electra 926.