I don't have any experience of JTS directly - personally, I wouldn't recommend anything but a Sennheiser EW300 or Shure PSM300 (with pro pack) as a benchmark (I'd take the Sennheiser over the Shure for the flexibility with the RF tuning - you don't get the same sort of flexibility until you get to the PSM900) but I do appreciate thats quite a price hike over the JTS.
I know that doesn't help you in regard to the level of the JTS perfomance - but the compander is such an important aspect of a wireless IEM system, especially for a bass player (e.g. the one on the PSM200 is so poor, it doesn't do any favours for people looking to get into IEMs as it eats all the bass and makes the top end really harsh... and you have no option but stereo) that I would say you should stay wired, or save up to push for a EW300. I think that everybody that has bought an EW300 on my recommendation will be able to confirm their performance is very, very good... but having tried other systems in the past, well, they weren't for me.
Are you wired at the moment (both from an IEM point of view and a bass point of view), or are you looking at getting into IEMs? The reason I say this, is that if you have a fixed budget, staying wired and investing in a decent set of customs will ultimately score you a better solution...?
EDIT: just remembered, you have just bought some ZS10s so I guess you are now looking at moving your IEM solution on.