My sense is that 12G would be a little high, even with a new panel and all. (Unless the house is huge – over 2000 sq. feet, say.) Shop around but be sure to stick with well-established electricians who know old houses and the code –– inside and out.
I imagine that bid was spec'd with 200-amp service. That's pretty typical and will give you a lot of latitude for additions later on. (Say, a 220V dedicated circuit for your Tesla Hot-Soccer-Mom-Mobile.)
But if you have a clear sense that the house need not accrue fancy-pants selling points, a 100-amp panel will probably give you what you need. If you don't need a hot-tub, that is.