Its kind of a hard question to answer. The only reason I responded is because I know Ayre and Vandersteen fairly well and have heard the SF's. No doubt you've heard that the Model 2's would be a good match for your amp. I agree, but you are the one that has to listen to the system. Ultimately, your opinion is the one that matters.
Generally speaking, if I had to compare the two speakers, I would say the bass in the 2's is going to be much better. Its a pretty easy call and I don't think anyone would argue different. As for the rest of it, the 2's will be more revealing and neutral. You will definitely hear more of what your amp can do. The SF's should have a richer, more forgiving sound to them. Forward, but not harsh. Kind of like ProAc. Changing to the Vandersteen, the sound stage will move back a bit. At first, you may think the sound is laid back, but that's really not the case in that there will be more detail and HF extension. For me, there's a "rightness" to the sound that I hear with Vandersteen that I don't hear with other speakers. Its kind of hard to describe. For me, its like comparing CD to records. You get a good CD player and it sounds OK. But after some time, you feel compelled to upgrade to a better model. So you get another one and it sounds better. But then you want a better one. And it goes on and on. With a TT, I can hear areas where I think the sound can be improved, but I'm not compelled to upgrade. I have no problem listening to what I have until I make a change. I know its an odd way to explain the speakers, but I can't think of a better way.
As long as the speakers are in good shape, you can always sell the Vandersteen's if you don't like them and get most, if not all of your money back. Also, I'm pretty sure you can upgrade them to Sig 1's (but not Sig 2's). Don't let that deter you, though. Sig 1's are extremely good speakers.
