Nice to hear that you've acquired the items that you did. As for "sell or not sell", I am probably not the best person to ask as I am biased towards the older gear. Everything that I have listed in my profile is cosmetically mint, and operating perfectly. I've had most of this gear for decades now. All of the Mac gear has been across Terry DeWick's bench at some point and still sounds great. That said, I personally have no desire or intention to replace or upgrade anything. Many will argue, justifiably, that Mac has far superior equipment available in terms of S/N, and features. But, at the end of the day I still have two incredible sounding systems in my home that meet all my needs. If I came across something interesting at a phenomenal price, I'm sure anything is possible, but I'm really not shopping for anything.
The C34 is a fine sounding preamp, with a multitude of very useful features. The MCD7000 when healthy is a fine sounding CD player. Both of these units will make a basis of a fine hi-fi system. I'm not sure what speakers you're using or what power requirements you have, but a 2500 is a monster. I can't imagine what you would do with that in a home (please enlighten LOL). Amps such as 2150, 2155, 2200, 2205, 2250 or 2255 would all be fine vintage options. Personally my 2155 has been a fine performer coupled with my ultra efficient Altec's. At one point I had a 2205 in my possession but found no sonic difference between it and the 2155. I ended up selling it.
Nice to hear that you have a Stereo 70. I still have mine, along with a PAS3-X that I've had since being a teenager. I've kept them probably more out of sentiment than anything. The last time I used the Stereo 70 was when the 2155 was sent off to Terry. Was nice to have it in action once again. I see you've got a nice selection of Marantz. My second favorite to Mac. I still have a 2270 in use, along with a pair of L100's.
Regarding the resale value of your McIntosh, best to look at sold eBay sales. Audio Classics is another point of reference but you need to consider that the restoration work they do commands a premium. Keep us posted on your decision, and let us know what speakers you're considering for this new system.