If you're asking this crowd for an opinion on whether or not you should risk insulting your sister-in-law by trading in a $300 down jacket for a fly rod you have come to the right place! You have our blessing and if she complains just get her to sign up here as a member and we will help her to understand your reasoning behind the swap and at the same time give her some hints for your Christmas gift.
If you are looking for specific rod advice, some of the suggestions already given are better than anything I could tell you since I stick to just a couple of rods and don't do a lot of buying, selling, swapping, demo-ing, etc. However, I will say that I think a 6 weight is a bit of overkill for the upper. 95% of my fishing in the Eastern Sierra is done with either a 3 or a 4 weight rod. The only time I break out a 5 or 6 is for very windy days or high flows when I'm going to be fishing big streamers and one of your 5 weights could probably handle that.