Part of MMM's message is about making conscious decisions about how you spend your money, as in, don't waste your money on shit you don't need, and if you do, don't do it mindlessly just for the sake of buying stuff.
Your husband may need a new amp or he may really, really want a new amp. Awesome. Good for him. If he has wads of cash to spend on a new amp, he gets to make that choice for himself. I don't know the dynamics of your relationship, whether he really expects that you would spend 3k on a Christmas gift (maybe there is a precedent for this type of spending, so he doesn't think this is a big deal?). If this really is the only thing that he wants, and rather than asking for a new tie or some plastic stuff he doesn't need, he put this out there for you to consider. IMO that doesn't mean that you have to foot the bill for the entire thing. Especially if you are working hard towards FI.
My husband lists lots of expensive things (we do exchange gifts, but I try to keep it modest and mainly stocking stuff), bigger tv, a newer camera. I won't buy that for him, he gets cash from his folks for xmas and b-day which is close, so he can pool that, and his monthly spending money towards that stuff. But if I can't think of anything useful for him, I will give him some cash to put towards it...even though it is our shared cash so it's a bit ass-backwards, but it basically lets him know that he can spend 100$ from the gift account for whatever he wants.
It's a gift, not a bill, so you don't have to spend that amount. If you can't afford to spend that much money, don't. If you don't want to spend that much money, don't. Its your money. The end.