One of the most important things about the rope is that it does not strectch. Many ski ropes do stretch, you do not want that when wakeboarding - you want to be able to load the rope to do the big tricks.
In terms of a tower, yes it makes a big difference. I have a 1999 18ft Bluewater. I researched towers for 6 months and finally decided to go for the Samson Sports (
www.samsonsports.com) tower. I have a few buddies with cheaper towers (like the Barewest) and pylon. The pylons get in the way and flex to much, the cheap towers are not strong enough when you start pulling bigger tricks and they look like crap.
Samson designed the tower to the exact specifications of my boat, it is rock solid, but can still fold down to fit in my garage. I added a sweet pair of Speakers and lights from Samson as well.
It makes a really big difference, the rope is pulling you up when you hit the wake rather than down like if you are pulling from one-foot off the water.
Good luck!