C49- or c8 preamp

I would recommend considering the C22.  I just purchased, updated the tubes - amazing. I am using a Levinson No. 333 amp. There pair very well.

I used to have C2600 - it helped me rediscover my love of music.

The nice thing about the McIntosh preamps is their internal phono stages are solid.  If you go with ARC you'll need a phono stage

Have both SS and tubes. To me, the bottom end on the SS Mac like the current C52 is tighter than the C2700 which is great for rock, jazz and blues but the latter seems to have a nice warmth and girth to the sound that the SS model does not have and it really comes through on music material like classical and vocals RnB. Both sound great and I find they shine well on specific types of music. 

I have briefly used both the C49 which is no slouch and the 252 integrated amp.  I really liked the 252 form factor ..... its retro and modern at the same time  if that makes sense.   I thought the 252 was great , I would imagine the c8 would be very good..   

I've never owned audio research but heard a lot of stories about failure and service that would make me pause.   I've had a few pieces of McIntosh , never a problem , sounded good and had strong resale.......  I wanted to buy a C22 a few months ago but couldn't find one and went in a different direction.     The new McIntosh gear is good.