For just riding I would say the AR1, that board is incredible! The thing is fast, skatey and very poppy. It would do OK at the cable but I like a board with an ABS rail to ensure that your edges stay solid after hitting rails etc.
I think the Webb board would probably be best. I loved everything about that board except for how it landed. If you decide to go Webb I'd perhaps try a larger board to help soften landings.
I've ridden my Union behind the boat and really liked it, if you go Union/Jib I suggest getting the larger size. My normal sized 138 Union feels like a smaller board, just in the way it rides on the water. It felt like I was going to bury the nose on a hard cut.
Best choice might be to seal up your Monarch for cable and get the best board for wake, if you are looking at Hype/Byerly, that would be the AR (or if you are like me, the Franchise).