I have swapped op amps in my V3 monos, Sparkos and Burson combination certainly sound slightly more transparent than stock...very subtle differences but definitely changes the presentation.
I have lowered the case temperature of my V3 monos substantially just by adding stick on heat sinks (available on Ebay and Amazon) to the top of each case. Obviously this would be impractical for Fosi, but in my system looks dont matter. No need for fans at all.
I notice Fosi sells a fan kit for the Monos. What's the consensus about needing the fans? Mine are getting warm, but nowhere near as hot as my Pass XA30.5. Clearly since Fosi sells a fan kit there is some concern about the amps running hot.