Well, an AC30 does a LOT more than just a Beatles sound. It's a very versatile amp.
The real key here is you said you wanted a contrast. If you've got your Marshal doing the bulk of the heavy lifting, than something different (like an AC30 or an old tweed Deluxe type amp) is going to fill in some areas which your Marshal simply can't do, and which any other high gain amp is going to have a hard time with as well. You don't even necessarily have to LIKE the second sound (though it would be nice if you did), all you have to do is like how they sound TOGETHER.
But hey, I don't insist, I'm just making a suggestion.
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