Disclosure: I'm a dealer for Cayin and Opera loudspeakers.
Unless your room is big (25 x 30, or more etc.), I would recommend against using sub with the Quintas. Natural and smooth sounding as they are, with bass extension down to 30hz, you do not need to use subwoofer especially your main interest is vocal reproduction.
We pair Cayin A-88T integrated amplifier with the Quintas and they are matched made in heaven in my opinion. We even use the A-88T with our Tebaldis speakers with more than satisfying result! And yes, you can use your preamp to drive the Cayin as well (it has Pre-in input). The A-88T offers 22wpc in triode mode and 45wpc in ultralinear mode. You can switch them on the fly during play. Price is $2100 retail. It popped up for sale used on Audiogon every now and then so try them.