The general consensus that I've heard is that you go with JL for quality, clarity, and longevity. You go with with Wetsounds for volume, and maybe just a step down in clarity and longevity. But I can only speak for my JL's.
If I were piecing a stereo together in your situation:
Step 1 - Amp the existing JL's. Even new Wetsounds won't sound any better unless there's an amp pushing them.
Step 2 - Sub and a second amp with volume control. It's going to add all the depth and richness you will lack with the smaller speakers. I think, depending on the amp, you can even isolate channels and control the volume separately if you wanted that option.
Step 3 - Amped tower speakers. I have 4 tower speakers on a 3rd amp with a separate volume control. This way I can crank up the tunes for riders via the tower. But, you could amp them with your other internal speakers if you have the extra channels.
Mine is a 2/200 watt bridged with volume control powering the sub. 4/400 watt with separate volume control powering the four 7.7" tower speakers. 6/600 watt powering the 6 internal speakers.
I'm an amateur at best when it comes to stereo equipment, but this system turned out great. Given the chance, I'd do it the same again. But, as I said before, I think you could go with either brand and be completely satisfied.