I have a KA-7300 that I'm using as a preamp. I like it real well. Nothing wrong with it but I may be able to obtain a Supreme 700C and wonder if I'd notice a difference, other than aesthetics.
Can't speak to the 7300 but the 700C is really a wonderful piece of gear. If it's not too dear I would sure be trying to get it. If it isn't worth it for you I'm sure you could sell it easily as they are sought after. .
No experience with the 700C so can't speak to SQ, but I'm also using a 7300 as a pre and I really think the aesthetics are similar. The 7300's preamp section is widely considered one of Kenwood's best so...............