[aceinc]

This is rather different than what I am used to doing audio wise. I am looking for opinions on what some decent speakers which would be period & class correct for a couple of McIntosh system stacks I picked up.

The two stacks I have are;

McIntosh: MC2105, C26, MR74
McIntosh: MC2205, C32, MR75

What I mean by period & class, is manufactured around the same time, and would be likely to have been purchased together (not too cheap, nor too expensive).

I have some speakers, as well if they would be suitable;

Koss CM1020 Rather impressive sounding.
Electro Voice EV Six*B, need their drivers refoamed.
Altec Lansing Valencias, sound OK, cabinets are somewhat distressed.

Also would a Thorens TD 145 be period & class correct?

Normally (and I may yet do this) I would take the best electronics and match them with the best speakers irrespective of the period & class.

[FullRangeMan]

Came to mind the vintage Polk SDAs system,
its was the only speakers I missing a long the
years, much better sound than any JBL I have listened.
There is an mint pair for sale in the Trading Circle now>
https://www.audiocircle.com/index.php?topic=183882.0

[S Clark]

Your Altec Valencias can sound much better than just ok.  With the right crossover, they can be very high quality.   

[aceinc]

Your Altec Valencias can sound much better than just ok.  With the right crossover, they can be very high quality.

I need to give them a bit more room to breathe They are currently too close together to really judge them.

I assume there are plans to create new crossovers, where can I find them?

Also I noticed the cabinets (at least the top) seems to vibrate/resonate with low notes. The cabinets seem to be made of pretty low quality particle board. Should I design a bracing system for them?

[Rusty Jefferson]

I have a couple acquaintances who have done some nice improvements to their Altec Valencia including damping the cabinets with a constrained layer to reduce resonances, among other things. One of them documented much of it here:
https://www.audiokarma.org/forums/index.php?threads/altec-valencia-heathkit-as-101.806226/

I think the Altecs will work best with fairly low power tube amplifiers that were ubiquitous at the time. Your 2105 would probably be a good match for some JBL L100s or 4311s and the 2205 maybe a pair of Magnepan Tympani panels if you have the space.

Me personally, I've given up on vintage solid state amplifiers. They aren't like an old point to point tube amplifier for keeping them safely running and I know too many people who have lost an unobtainium driver(s) to a old solid state amp taking a dump.