Sorry for the story here but....
Several years ago I was looking for that MOP era tone, living over in the UK, the choice of Boogies isn't as big as in the US.
I bought a Mark IV but just couldn't get a good sound out of it apart from the cleans. People always say that Boogies aren't plug and play and you need to tweak. Well I spent over a year tweaking without success. Eventually I sold it. I'm used to oldschool Marshalls (UK thing!) and I just couldn't get on with the the compressed tone, simul class and not being able to change the bias.
I have always like the sound of the Mark II, it has that raw, less compressed tone compared to the IV. I would have probably bought a C+ except I just don't like Boogie power sections and of course the cost!
So anyway, a Quad popped up on ebay for cheap a couple of months ago - these things are extermely rare in the UK. I couldn't resist the prospect of being able to match a IIC+ preamp with a Marshall poweramp.
I paired it up with a Marshall 9100 with NOS Sylvania 6L6GCs (yes I can bias this thing!) and I love it to bits. It is plug and play, OK I am used to the Mark controls but it reacts in the way I want, the tone I want is always available. There's no constant tweaking, it just sounds excellent whether it's cleans, metal, rock, blues strat or flying v etc etc.
I have never heard a real IIC+ but playing along to Metallica, especially live stuff, it seems identical.
I'm amazed these things are so cheap, maybe it's not widely known that they are a IIC+ and III in one.
The only thing I would say to be wary of is they are complicated beasts, make sure it's fully working. If something goes wrong, it'll have to go to a good tech to resolve.