Re: Fender Twin Reverb
If you buy a Twin, you're buying it for the Fender tone. Why change it so much by trying to turn it into a different amp? The OCD, the EHX East River Drive (808 style drive pedal), or the like is probably a better candidate for keeping your Fender tone intact, but adding some hair.
The whole idea of a dirt box is to change the character of an amp. Otherwise, we'd all be running our Twins and Plexis on 10 for our distortion (Or Vibro Champs), and have to have a storage locker full of vintage amps. Not really practical, is it?
Like I said in my post, I can easily see using several different types of distortion boxes through a big clean amp like a Twin. There's nothing wrong with keeping your Fender tone intact, I would never argue against that.
But the OP said he's doing a lot of '60s and '70s classic rock, and a lot of that stuff was done with Marshalls. (And Vox amps, too!) With so many GREAT pedals that emulate the tone and feel of these amps, why not get a variety of pedals, including a TS or a more transparent OD? (The Soul Food comes to mind.)
My goal is to serve the song. Even with a great amp like my Mesa Mark V, I can't get that buzzy distortion as recorded on songs like "Satisfaction", "In-A-Gadda-Da-Vita, or "Hello, I Love You". So it makes sense to me to get a FUZZ pedal like the EH Satisfaction to get those tones (or something close to it)--to serve the song. It all depends on the OP's repertoire. If I were doing a Motown Tribute band, I might not need a dirt box at all. If I'm doing AC/DC songs, then I'd want a pedal that can get me Mal's crunch rhythms and Angus's snotty, in-your-face, lead tones.
The Twin is a great platform; you can do a wide variety of music on them, which is why you see them on stages all across the world. They're powerful, toneful, and they do a great job of taking pedals. Adding a MIB-style of pedal, or fuzz, or TS, or Vox emulator, is only going to add to that versatility.
Bill