yes it is less power but you will not notice the change in volume you think you will...I battle with my Twin all the time...Twins are simply loud ass amps, and if you are looking for crunch a Twin should be the LAST amp on your list...
Yep, although if it's a master volume Twin, changing that to a post-PI master will probably help out some, as will changing the PI to an ax7. DNK if that will really get you into SRV territory, but it will get you closer with less volume.
Fender has a new Vibroverb Custom that has similar mods done to it the same way Cesar Diaz modded SRV's Amps. It might be a better way to go. The Twin is very clean and very loud. That being said you can get a good SRV sound with the right pedals. A TS9 will be essential. The Super Reverb would be another good choice.
Twins are very, very loud and clean amps. Heavy too! I would not own one again myself. Just to loud and to hard to control. Get a smaller amp like a Deluxe Reverb or Vibrolux Reverb. Lew