For sure make the extra investment in the MA6600 for the fuller "McIntosh" sound and the extra power gives flexibility for future speaker changes, particularly as you are already considering moving to larger Diamonds. BTW, while the MCC201 is a very good sounding CDP (I enjoyed one for a year), be aware that some of the MCD201 units had operational issues -- albeit fixable by the McIntosh factory.
Newbie Needs McIntosh Help
I own a pair of B&W 805 Diamonds, looking to upgrade to a McIntosh system and need some help choosing an integrated amp. Stuck between buying a MA6300 and a MCD201 or a MA6600 and continuing to use my existing CD until I can upgrade the CD. I'm thinking the MA6600 over the MA6300 for the future in the event I'd like to upgrade the speakers to larger diamonds. Would like to stay with McIntosh. Thank you!