Engine question… Pro XS and Etec HO questions.

Ok. I have my rig sold suppose to meet the guy sunday for pick up. Now I am looking for a good used rig. I have experience with a 225 Pro Xs from my 2008 Cougar. I have a litte experience from a very brief ownership of a 09 Z520 that had a 250 Etec HO on it. I like the Pro XS ok it performed well had good holeshot and decent on fuel. The HO loved gas and was slower out of the hole but this isnt a even comparrison due to it was on a tub of a boat. So I am asking for QUALIFIED opinions. How will the HO do on fuel compared to a Pro XS on a Cougar or Puma? I am going to buy a nice used rig soon and these are the motors I will most likely choose from. I have a couple of boats that I have my eye on on with a Merc and one the HO. Will the Bass Cat hull make a great difference in fuel economy and holeshot on the HO? I mean I want it to get 4mpg or better crusing 4,300-4,500 rpm at 50-55mph. I knw the Merc will do that but honestly will the HO? I dont want another gas hog but if the boat makes a big difference I would consider a Etec. My price is 30k or less I would like to find a 2008 or newer Cougar FTD in that range. I ahve found a boat with a Etec thats just what i want in electronics and accesories but like I said it has a HO on it and if its gonna drink gas like the one on the ranger did im not intrested. Also does anyonw know how much it is to buy a extended warranty from Evinrude? The etec warranty expires at the end of 2011 and I want something with atleast 2 or 3 years warranty. I will buy a boat with a 250 Pro XS or a 250 Etec HO. I am just trying to decide if the Bass Cat boat will improve the performance and mileage a good deal. Thanks for any input.