AWD vs RWD
 

is it worth it to get the AWD option on the CTS???

Yes.... guess it depends on your weather.

I live where there is snow and ice for about 5 months of the year. I bought Nokian winter tires for one rwd car that I have and that made it clear to me that it is totally unnecessary to have AWD.
In certain jurisdications (Quebec) winter tires are mandatory regardless of whether you have AWD or RWD so whether you need winter tires depends on where you live.
If you live in CA, AZ, FL, TX or NV, I don't see why AWD is required. It used to be limited to off road vehicles but the manufacturers have used it as another marketing tool on which the make a profit.
Save your money and if you don't know how to handle a rwd car go to a perforamance driving school that teaches rwd car control. If you live in snow country you already probably know how to handle a rwd car.
RWD provides better mileage because it does not have approx 250 lbs of gears, etc that is the AWD.
AWD provides another mechanical component to be defective during your ownership period.
Are you going to get the non-slip differential that should be standard on all CTS's?
If you live in pothole country like me, you'll want to consider that 45 aspect ratio tires are meant for places with great smooth roads...not places with potholes where rims and tires are trashed.I don't think that active handling is a replacement for non-slip differential.
The 19" 245/45 do not provide enough sidewall IMHO for winter tires.

thanks all for your replies, really appreciate the advice.