McIntosh looking for recommendations

I’m relatively new to higher end audio and would like some recommendations from fellow McIntosh owners on the next piece of equipment that I purchase. Currently I have an MAC6700 that I’m quite happy with. However I’m also ready to add to my system with either adding a C2500/2600 or a MC452 to it. My question is which of these would change or have the biggest impact to my system?
I either listen to CDs or stream my music. I have a MCT450 transport and use a Auralic Altair. My speakers are Maggie’s 1.7i’s. Thanks in advance for all feedback. Also I want to keep the MAC6700 for now and try to use it as the preamp or amp.