Hi Andrew,
The prices you have seen are typical. Look carefully and take your time, you will have a good choice - but the old adage, you get what you pay for is true often - I would bet the 11k boat is older, not fitted out as well etc, etc as the 13k boat.
I had a MkII 165 for 3 years, now have a 175. The 75hp is the best engine choice by far, the 60hp can struggle a little. Etecs are fantastic.
As for the coloured hulls - I had the blue one. Look very nice, but they scratch very easily and are hard to touch up. I now have a white hull which doesnt show at all. You choice - bit like black cars really!!
Try and get as many extra's as possible. A decent plotter / Fishfinder is worth a lot - you'll be surprised how much you can spend fitting a boat out. Also things like canopy, SS radar arch, bait rails etc are often areas owners skimp on and cost a fortune to retro-fit from Warrior.
HTH
Adam