I have an all original 1x12 100watt , no Simu Class Mkll C-. I am thinking about having Mike B at Boogie doing the C+ update now, before the guy retires or stops working on amps. I understand there aren't many C-'s that have not been updated. I also understand that the C- has somewhat better cleans, while the C+ has a much better dirty channel. I like the way mine sounds, but have heard C+'s and like them too. My question has to do with current and future value. Leave as is and have one of the few C-'s out there, or have modded by "the man" (MB) while I can? I plan on keeping it for quite a while, (although for the right price...), but as with any of my "vintage" stuff, look at it as an investment as well.