9 watts will be twice as loud as 5 watts.
Tube crunch at a low volume: everybody wants it, few or none ever really get there. Either it's still too loud or with an attenuator or master vol it now sounds weak and dull.
There's no way of knowing which amp sounds best without hearing them...
Pedals with tubes and big claims come and go. I've seen dozens over several decades.. Amps based on Fender amps from the 50s have been around as long as electric guitar and are still here.
Hmm, I wonder which will have staying power?
Yeah everybody here says a twin isn't too loud, master volume, overdrive pedal, blah blah blah.
Yet I NEVER see any one using a sf twin except once in awhile a major label country guy....no not even them. Or plexi front Marshalls either for that matter.
Dude, do you need an amp that's as heavy as a boat anchor and so loud you can't play it ANYWHERE? Why do you think deluxes are $4k and Twins are $800.
Great amp. But not practical for anything unless you just joined an Allman Brothers tribute band that plays outside in cornfields with no PA support.
Here's the REAL ANSWER.
It would be best to cut the head box in half and add what you need to the middle.
Or just leave the middle open. The chassis bolted to the 2 pieces would hold it all together.
Post pics when you are done.
I don't have any but if I did I would put them in a vault and save them for when we get the 20 minute warning of the end of the world. Then I would throw them in any fender I got laying around and blast full volume until the world was vaporized in a cloud of 6L6WGB sonic ecstasy.
These have been the only amps I've gigged with for the last almost 5 years. Don't let anybody tell you these are toys.
Hint. If you use it alot in a gig setting you are going to need to replace those el84s about 3 times a year. It's the vibration from the speaker that rattles them to death. Buy...