Every MC I've owned has had the base engine and I've felt that all of them had plenty of power. You have to remember that in this high end tow boat market putting any product out there that is under powered would surely hurt the company's reputation. You can't make that same statement in the I/O runabout market. I honestly can't remember a time (like when I had I/Os) where I thought, gee I really need the bigger engine.
I believe the 89 TriStar had the 240HP Ford 351 which was the standard engine and was plenty power for that boat. The 95 MariStar 200VRS had the standard 275HP, never thought for a moment it was under powered. The 03 X2 had the RTP, no issues with power. The latest 07 MariStar 200 has the stock RTP and again I can't think of a time where I needed more power. Now saying all that if I would have run across any of those boats with the bigger engine option I would have jumped on it. The MCX is really pretty, just didn't come across a good one when I was looking. It seemed like every time I did come across one there was something wrong with the boat that made me pass on it. I personally agree with mccobmd, don't let the RTP be a deal killer on a great boat.
I've had Perfect Pass on the last two boat and it is a must have option for me. If the boat doesn't have it don't sweat it, it's easy enough to add especially on the newer boats. My 03 X2 didn't have it when I bought the boat. I purchased my PP on line and had it installed in about an hour and a half. Other than the servo motor it was pretty much a plug and play installation.
I'm a recreational slalom skier but I know some really good course skiers that I had ski behind both the 03 X2 and the 07 X2. The 03 had the better wake between the two. I've read that the wake plate option on the 07 can really help with the slalom wake but I don't have that option. I skied regularly behind the 07 X2 this summer and didn't really have any problems at 15 off. My complaint would be that there is more spray and the wake itself is rather large for a ski boat.