How much space is too much space?

I've always hoped to move out of this house into something newer, better laid out and larger. I've begun looking, though we still have no clue what we could sell this house for, so it's all still a lot of window shopping.

One of the hits in my search is 3,920 sq. ft. of living space. I think this is too much. That rooms would just collect clutter and our heating would be more of an issue (it also has two kitchens, which I don't really want any more.) But I was wondering what other people thought. The way the pictures show it, they have kind of a party area with a bar and pool table. (This house is still extremely tempting, since it's with in walking distance of a lake which I believe has swimming!!!)

On one hand, I collect a lot of stuff and would love a library, music room, craft room and shop, but on the other hand, Greg and I tend to spend most of our time in one or two rooms. Part of wanting to upgrade is to reduce our heating costs and get rid of some of the problems of owning house which has a lot of maintence issues.

Anyone have any sage advice. Part of the problem is I don't have a good feel for square footage. We were recently shocked to learn we'd been lied to when we bought this house. They had told us ~1,800 sq. ft. when we're actually ~1,500.

On the other hand, I'm trying to decide if 1,900 sq. ft. would be enough for us. We really hope that this will be our one and only move, as long as Greg's work stays in the area, so we want to plan for a house that will suit us for a long time (but with still no plans of kids.)