To answer your questions, in order:
The speakers were originally Sunn 108 guitar Transducers.
No.
None that I know of, and I wouldn't recommend it.
I don't think it would add low end at all.
No, but if you crank it, you should be able to really cook!
I don't know.
150 watts into 4 ohms.
The power amp section is, but the preamp section is different. For one thing, the Lead has two channels.
Yes.
There's nothing special about the footswitch. I use one that came with a Peavey practice amp.