I agree that the MA6300 isn't needed any longer.
The C2500 is a tube preamp with MM/MC phono inputs and a DAC section - that is the enhancement over the C2300. C2300 sounds wonderful (to my ears anyway) and was very well reviewed.
C48 and C50 both have MM/MC phono and DACs; C50 has more EQ bands and gets meters. Not sure if there are enhancements to the DAC section in the C50 over the C48 - haven't checked the specs. My C50 is one of the best purchases I've ever made.
Note the pass-thru feature could allow you to send variable output from the D100 directly through one of the preamps. That could offer you more flexibility than you currently have.
All units are in current production, so you can easily compare specifications on the McIntosh Website.
The C2500 is a tube preamp with MM/MC phono inputs and a DAC section - that is the enhancement over the C2300. C2300 sounds wonderful (to my ears anyway) and was very well reviewed.
C48 and C50 both have MM/MC phono and DACs; C50 has more EQ bands and gets meters. Not sure if there are enhancements to the DAC section in the C50 over the C48 - haven't checked the specs. My C50 is one of the best purchases I've ever made.
Note the pass-thru feature could allow you to send variable output from the D100 directly through one of the preamps. That could offer you more flexibility than you currently have.
All units are in current production, so you can easily compare specifications on the McIntosh Website.