paddymac and vpar
For me (75kg give or take) sailing mainly at Dutchies which is not a wave venue the Rider 100 quad wave board has been one of the best windsurfing purchases I have ever made.

I have used it with a 5.9 S1 and a 5.3 blade/ now 5.4 Loft Purelip (pics in sequence, top 2 up North and last one down South)
It is not as fast as a FSW but I have changed my sailing dramatically so I am often out in float around conditions that I would not have left the beach in working on tacking and sailing upwind off the plane and catching small lumps then when it reaches 12+ knots I am rarely sailing more than 200m offshore and working on cranking gybes that I would not manage on a FSW as well as turns in the mush. It gets planing faster than a smaller wave board but does need good technique to get the best of early planing. This means that you can get nice little jumps off the inside section.
In the odd opportunities that I have had to use it in real waves it performs so much better than the FSW I have had in the past and I have been out in some sizeable (for me) swell. It is not as comfortable when the wind gets up in choppy conditions so I don't sail much out the back.
If you are looking to improve your sailing in proper waves I would definitely agree with Ivan and say go the full on wave board but be prepared to change how you sail and travel. If you are normally sailing in less than ideal waves a board above your body weight will get you out practising the skills you need when you get in to real waves. If you have a FSW you are more likely to just go out for a blast and not do so much turning.
Also strongly suggest doing some courses. I am a Cribby fan boi but my wavesailing and general skills have improved greatly since doing his courses. There are other coaches out there as well but try and find someone that you connect with and stick with them.
You guys are welcome to give the board a try.