Congrats, you'll love them
Price sounds about right compared to what I paid for mine, Also 27's.
As far as power loss if there was any it was barely noticeable when I put them on my 650, now the same ones are on the XTZ and can't say there is any power loss what so ever.
I've had one puncture from a railroad spike on one of our trails up here, but the spikes have claimed every type of tire made.
You'll love the handling, ride, and durability.
2010 Prowler XTZ 1000-
27" Grim Reaper Tires/Home Made Roof/Arctic Cat Mirror/Quadboss Folding Windshield w/ home made support bar/LED Tail-Brake lights//Venom 4000 lb Winch/Amsteel synthetic line/Home Made Doors/Custom Adjustable Seats/Custom Oh Crap bar for passenger/Tonneau Cover/Fat Max storage Box in bed
Tiger Tail Towing system