Well, my journey began with McIntosh in 1990 with an MX-110 and an MC240. For the next decade, I tried nearly every flavor of vintage Mc (and some vintage Marantz) there was. It was certainly a fun ride, I had some great pieces, and always had great sound. Today, I'm no longer messing with tube gear as I simply don't have time for the maintenance. [My MC225 is once again collecting dust . . . ] It will always have a special place in my heart though - especially the MC60s and Marantz 7c preamp.
Personally, I never recommend purchasing gear based solely on what you've read on the 'net. We all have different preferences. You really should consider a road trip to visit a Mc dealer and see, feel, and hear the stuff in person. A C2600/MC452 would be about as far from a C11/MC30s as you could get. You may not like the pair at all compared to what you're used to. OTOH, you may fall in love with the stuff. Keep in mind that many consider the MC30 to be the pinnacle of McIntosh amplification of all time.
Have you considered simply buying a modern preamplifier and using it with the amplifiers you do have? [Even today, I think the MC2105 is still a very capable SS amplifier.] That would allow you to get your feet wet. If your amps are performing to spec, there is no question that a modern Mc preamp would best any of the vintage preamps - noise, switching, ergonomics, etc. - and your amplifiers would have never sounded better. Only you could say if an MC452 was better than your MC240, MC30s, etc. in your system in your space.
Modern gear won't need you. Set it up, turn it on, and listen. When you're done, turn it off. Even the new tube preamps are very low maintenance. Have you considered how boring that may be compared to owning gear that requires your constant attention to perform to its fullest?