Well I have the 650C CD player and it is superb. What you partner it with really depends on what sort of sound you prefer.
I used to have the Mezzo 2s with the Cambridge 740C and 740A and the combination was very detailed and precise but lacked an element on musicality. Somehow, despite being superb in many ways, the system didn't pull me in.
I have briefly tried a 650A amp (for about 3 weeks) and found it to have the same strengths and weaknesses as the 740A so I'd imagine your proposed system will have similar traits.
If you would prefer something less clinical I would suggest using the 650C as a starting point. I've owned the NAD C545BEE and extensively auditioned the Marantz PM6003 and I personally think the 650C is the best sub £500 CD player. As I type I'm listening to mine with my Arcam A18 amplifier and Dali Lektor 2 speakers, all hooked up using Chord Company cabling - approx £1300 of system - and it achieves a great balance between detail and seperation, and sounding involving and musical.