The supersonic is a great amp.. I have been playing for 35 years now and I have been fixing amps for 24 years. I got my hands on the "new" Supersonic 60 schematic and noticed there was only about 10 changes in parts values between the original amp I have and the new supersonic 60 amp.. I did the changes and the difference is NIGHT AND DAY. The clean channels are now balanced.. And the amp does have more bottom end on the clean channel. The reverb is also better. If you are serious about keeping your Supersonic Contact fender get the Schematic for the SS60 and make sure its for the SS60 amp not the SS. Get the SS schematic while you are at it and you can see the changes for your self.
I break the speaker in by hand using my thumb around the surround breaking down the paper but not going through it with my thumb
I also soften the spider on the speaker by hand.
I use the following tubes
Tube amp doctor 6L6WGC
Tungsol 12AX7 for the preamp I might try something new for the overdrive channel.
I use NOS Jan Philips 12AT7 for the phase inverter and reverb.. i make sure the sections are matched for the inverter tube I deal with the tubestore.com for all my tube needs.
After the parts are changed the amp sounds great. Enjoy.