Any 5.5m RIB with enough fun numbers on the transom will pull a skier ok. Bear in mind the following:
1. You need to have a rearward facing seat for an observer to keep an eye on the skier. Jockey seats are ok for this and side-by-side jockeys work better than a 2-seat inline jockey console, as the observer can communicate better with the boat driver.
2. The driver may wish to have a ski mirror, so check whether one can be accommodated on the console.
3. A high tow point is preferred by wakeboarders, to get good lift. If you intend to tow off an A-frame, make sure it's man-enough to cope with the linear and lateral forces imposed by a skier/wakeboarder.
4. If you use a bridle rope off the transom U-bolts, check whether the rope fouls the tube ends when the skier is carrying out slalom turns.
5. Ski storage is rare on RIBs. I once set up a ski locker below the deck, which was useful. Ski/wakeboard brackets for hardboat wakeboard towers can be fitted to an A-frame.
6. Not all skiers are able to clamber over the tube when they've finished, so you may want to think about a boarding ladder.
I run a 5.8m Vipermax with a 150 Opti and tow skiers/wakeboarders from a bollard fitted to the top of the (2") A-frame. The set-up works well for skiing and wakeboarding, as the motor copes well at low-medium speed for wakeboarding and is also good at higher speed for skiing.
If you take badbaws' advice and go for an SR5.4, you'll probably want to seal off the flooding hull system, as this really slows down the planing time, which is a PITA for a skier. The SR5.4 also fails on lots of the above points, so I'd be inclined to go for something different, if skiing is going to be high on the agenda for the boat.