I disagree with Jason's assessment of the wake, but that does not relate directly to the OP's question. Jason just needed to go a little faster, weight the boat differently and change the rope length...all factors that are very important, but are very easily fixable.
My 45 has the 8.1, but I have been in an X35 with the 350 MCX which weighs the same. It performed well, but I would not expect to heavily weight the boat over stock and drive 40+ MPH. 35 MPH would be easily doable, IMHO, and the hole shot would be a little sluggish until you got the prop Mikeski recommended.
I would expect you to get a good deal on it. The 8.1 L engine is a $14K upgrade and the LY6 is somewhere around a $5K upgrade on a new boat. So factor those in when comparing boats.
(Message edited by talltigeguy on December 30, 2009)