Excellent points to consider. Touring is probably the farthest option away and would be the ideal bike to replace my Sirrus as a commuter, so I'll save the touring frame for later.

After talking with one of my cat 3 rider buddies, I got the idea of potentially doing a 3 bike lineup - Sirrus as the commuter, pure road bike and pure mountain bike. This way you have 3 bikes suited for their exact purpose.

I think a higher end cross bike would do the job just fine on the road, but to take it offroad, I'm not sure if I'd need a different cassette and wheel set to go with beefier tires.

Thus, here's the simplified math I'm using. Since I'd need to get shoes and pedals for either option and 1 set would do, those cancel each other out.

Ideal Riding Scenario
Commuter - 3-5x/week
Road Bike - 1-2x/week
Mountain Bike - 1-3x/month

Option 1 - Road and Mountain Bike

105 Road Bike - $900 to $1300 (Trek 1500 to Specialized Roubaix/Trek Pilot 2.1)
Basic Hardtail MB - - $350 to $550 (Specialized Hardrock to GF Marlin)

Total - $1250 to $1850

Option 2 - Cyclcross bike with 2 wheel sets

Bike - $900 to $1500 (Bianchi Volpe to Redline Conquest Disc)
Changing cross tires to road tires - $30 to $50
Second wheel set, tires, cassette - $200 to $400

Total - $1130 to $1950

So overall, it seems that for the same money, you could get 2 bikes ideally suited for their intended purpose rather than use a cross bike to try to hit both ends of the cycling spectrum.

Looks, like I'm test driving the road bikes first. I'll look at mountain bikes second and years down the road, I may switch my Sirrus to a cross or touring bike.