As a fellow Seattle-based skier, I'll throw my 2cents in. . .
Fwiw, I've been going with 2 primary skis for the last couple of years, Bonafide/Bent Chetler (with some race skis and some other assorted selections thrown into the mix). So I think that your basic instinct is correct - if I could only have 2 skis, it would look something like 95-105 as the all mountain ski and something wider, 120+, as a dedicated powder ski. At least that's how I've been playing it.
This also assumes that you are keeping your Rossi's for super firm days (like December - mid-Jan last year), groomers at Mission Ridge, etc. .
Width of the daily driver depends a bit on how you are slotting it in the quiver and where you are skiing it. And of course, what you prefer in a ski day.
Because you are also investing in a wider ski that is dedicated for powder and fresh snow days, I think that something strong'ish, with metal, ~98, at would be the best complement to a powder ski for around here. More nimble, more fun - a better ski for Alpental, a better ski for bumps and trees than the mid-100s.
Another one to consider in this slot, if you are inclined to go narrower and more hardpack-biased with the daily driver, is the Fischer Motive 95. Fischer doesn't get much love in these parts, but I thought the Motive Series was awesome during the demo days last spring. I could see the Motive 95 as a Bonafide replacement, a bit more traditional in shape, a bit more technical - kind of a poor man's FX94. It has a quicker, lighter feel than the Bonafide but it is less loose because the tail is more traditional - so it would reward good, burned-in race technique. I think it would be a killer daily driver for the Alpental/Hyak skier and a great firm day ski for Crystal or Stevens.
So where do you ski locally? The background in the pictures seems too bright to be one of the home hills. Mountain and terrain matters. For example, if you intend to keep the Rossi's in heavy rotation, and you ski a bigger mountain like Crystal something in the mid-100s could be the choice for your all-mountain slot. You mentioned the Cham 107 and if you liked the feel (which is rather particular, so you probably want to demo first), it could be an excellent Crystal ski. Similar ideas are the Cochise which I think is an awesome Crystal ski (chair 6, North/South on softish, chalky days) or the Supernatural 108 or the QLab 104 (I loved that ski at 183 last spring - it is a powerful ski that of kind of splits the difference between the Cochise and the Bonafide). All of these would still be workable at a mountain like Alpental on a softer day, but something ~98 like the Bonafide (a bit more narrow, a bit quicker) is better in that venue.
As for the powder ski, I'd go wider (120+) if you are picking up an all mountain ski in the slot below. Especially at your size. A ~98ish ski can migrate up into deeper conditions, and the powder board can migrate down as long as it is soft. So even with a spread of 20-25mm you have enough overlap in capability that your choice at the car in the morning will generally work out for the day.
Of course you don't need a powder ski, but they are really fun and you would use it a decent amount in a good season here. It isn't necessarily the right tool for the job every day, that said, you don't need 2 feet of blower before you pull them out either.
There are a ton of great skis in both categories. You can't go wrong. I'd swing by your specialty shop of choice and talk it through with the staff.
Have a great season and hope for snow.