jcn3

As was mentioned, C OO means Cornwall Oiled Oak. According to this post, RV2 refers to being shipped with a riser. From the serial number, the first two digits are the year -- so they were built in 1989. I would like to see the tag and anything stamped into the back edges to confirm, though. Note that if the back is not removable then they were definitely built in 1989 (i.e. they're Cornwall IIs).

with your amps, i would think something like the evo 200 preamplifier would be the natural choice. if you want a tube pre-amp with a no nonsense look like the holman, then a quicksilver remote control line stage would be a good choice (https://quicksilveraudio.com/products/rc-line-stage-preamp/). don't think you're going to find any tube preamps with dsp built into them. the workaround is to get something like a mini-dsp and use the tape loop on the preamp. (https://www.minidsp.com)

i demoed the evo 400 integrated at one point and was amazed at the amount of heat that eight tubes put off. frankly, i think that the evo 400 is way more power than needed for your forte ivs. have you considered the evo 300 or even (what i consider to be the bargain of the century) quicksilver mid monos? the mid monos won't win any beauty pageants but they are really nice. https://quicksilveraudio.com/products/midi-mono/

the size of the room is a significant factor. i used quicksilver mid monos (~30 w/channel with el34s) that sounded awesome with my chorus 1s in a medium-sized room. also, power supplies and/or output transformer design make a big difference in how amps sound -- it's not all watts.

where are you located? what finish are your chorus ii? can you post some pics? actually, would be better to post this in the garage sale section.

the last year that serial numbers were stamped into the cabinets was 1983 (with a "Y" in the serial number). after that, as @wuzzzer said, they were just on the labels.

the sonos amp will work, but the hk amp you mentioned would be better with the heresys. plug a sonos port into the hk and enjoy. an even better option would be to use a bluesound node for the same money.

those are insignificant temperature differences. AND those temps are nothing. why are you so concerned with this? you definitely should be concerned with loss of hearing.

i would not use a sonos amp with your heresys -- i don't think it would be a good match. you're better off with what you have matched with a sonos "pre amp".

the "y" means 1983. sounds like you've done all you need to do to the speaker. whether a heresy ii or iii or iv sounds better than you speakers is personal. "most" would say the iv models sound the best -- personally i preferred by 76 heresys with new factory caps. your heresys can sound quite good with the right amp and set up properly. i'd sit back and enjoy.

so you're saying the link doesn't work for you? i think you'll need a google account for it to work. works for me.

if you're talking about older forte risers, they were the same as the chorus in design, obviously different in terms of dimensions. PWK used the enclosed risers to help reinforce bass -- he didn't want the heritage speakers to be suspended on stands, compromising the bass. you can have them built like they originally were or like they are on the current fortes (leaving about an inch of overhang on the front and sides.

seems a bit steep for raw birch.

Best of luck. Hoping for a full recovery for you.