I'm looking to supe up my '65 Twin reissue and speakers came to mind as the first mod to do. Can't afford the Blues, so I'm entertaining the idea of loading in some Greenbacks. These seem to be a pretty Marshall-specific speaker, though, so my question is this: will I be sacrificing any of that sweet Fender clean by replacing the stock Jensens with Greenbacks?

I don't think the Greenbacks will handle the 85 watts the Twin dishes out. I have 25 watt Greenbacks,I am not sure if they have different power handling ratings. If you like Celestion Blues (rated at 15 watts) try the Celestion Golds. Another great speaker is Tone Tubby Hempcone speakers. I would recommend doing some research on those. I think the guy in Los Lonely Boys uses the Tone Tubbys in his Twin Reverbs and Santana likes them cause they are made from hemp.

Ah, I see. What's the general line of thought in terms of the speaker wattage-amp wattage relationship?

Will check out Tone Tubby. Everyone like a little hemp now and again.

I run Greenbacks (always have) in my '85 Red Knob Twin.

I tried Vintage 30's and Celestion Neo Classics in the thing, and the Greens are the way to go.

Actually in the past few months I've changed it up to One Green and one Neo, and I LOVE IT! I got the same going in my AC30.

There is a really nice speakerbreakup that the greens give you, it helps drive things a bit harder, and it cleans up the top end sparkle a bit.

I'm a big fan, and since my twin don't go up past 4 most of the time, I think I'm safe

I'd check out Weber Speakers if I were you. They have lots of different speakers and their take on the Blue is pretty amazing.

This is what I like about the Line 6 stuff, you can try any speaker in any amp and out of my experience; I'll vouch for Greenbacks in most anything! Then again, I try to compete with a classic Marshall (well, emulated) tone and Greenbacks vs V30's just kill when together in a mix. Greenbacks have the nice lower mid emphasis (that I boost with a tube screamer as well) and V30's have the higher mid more classic tone.