OK, hold up here.
Are you seriously considering buying an amp that costs 1-2-3-4x the price of the speakers you're using with it? We're talking a tiny fraction of an improvement at best, particularly with M2s. If you were driving big towers, like M80s or M100s or something at high volumes, well, then, sure. But M2s? They're bookshelves. Best suited to not so high a volume. Any improvement you see from changing the amp is so marginal that it cannot possibly be worth the cost.
Here's my philosophy on amps:
1. High end, well engineered (ie, engineered to amplify evenly across the spectrum) amps will sound the same at the same volume level, assuming the capabilities of the amp are not being exceeded at that volume level (ie, the amp is not clipping)
2. Amps that are engineered to sound different (ie, NOT flat across the spectrum), will probably sound at least somewhat different. Tube amps fall firmly into this category, unless they're massive and designed specifically to be flat. Then you might as well buy solid state.
3. The amp is really not the place you want to be modifying the sound! If you want a tube sound, it seems likely to me that you'll get more tube sound for the buck from a tube pre-amp. That way, the coloration is amplified.
4. Marshall amps sound great because they are being overdriven. Do you want to be overdriving your amp? Or do you just want to let the musician do it for you?
