I have the 2014 version of this trailer. There's only a few Optional items even available because these Model's are Loaded from the get-go.
Advantage Pkg
Touring Edition 5.0
Free Standing Dinette W/4 Chairs
Champagne Hi-gloss Fiberglass
I have all of those options. The Slide Toppers you refer to are in the range of $3600.00 installed. $1200.00 each. Not sure about the tires you refer too as far as cost.
Like others will say, YOU have to be happy with your deal. IMO you're up near a $50,000.00 MSRP.
One thing I did do because a 12 foot awning on a 37 foot trailer is way to small, I paid to have an identical 12 foot electric awning installed directly on the FACE of the front slide. $2200.00
Then comes the Interior and Exterior Protective Treatments and the 5 Year Extended Warranty. Things add up.
IMO you're CLOSE...
Hope you're not gonna try to tow this with a 1/2 Ton truck???