The right amp to biamp with McIntosh MC275 Mk V?

A further look into the Spectron manual revealed that if you run this amp unbalanced the gain will dip to 26 db-a perfect match for the Mcintosh in unbalanced mode.They are both in Harmony now and the listening test lies ahead.A few hours today reveal a really good match.Now i can listen to both together,a tube amp by itself,or the mighty Spectron exacting judge,jury and executioner to all that lies in it's path.
Sometimes you have ask a question to get the answer you had all along.Great listening to all!

Hello, I see all these references to McIntosh MC275 different versions. I wish someone could run thru (for me) any chronology and what the differences are (how to tell one version from another). The versions I am aware of are:
1-I'll lump all amps made during the 60's and 70's as ORIGINAL.
2-The first reissue that I know of (a "Gordon Gow" edition)
3-An edition where it has the plastic barrier strip, gold balanced inputs, RCA's below, and black gain knobs, etc.
4-A version where speaker oututputs are newer binding posts for bi-wire, gain knobs are removed, etc.

There are probably a few versions I may be describing here, so any info on full list of versions and or links to that info would be appreciated!

I don't know all the history, but the Mk IV vs. Mk V:
IV has a splitter tube, and gain controls. V doesn't.
IV has speaker terminals that only allow spades. V allows for bananas.