The JD design is one of my favorites in the knife world. I own all the different JYD models except for the true customs which I've never seen for under $2000. Kershaw's SG2 model is an exceptional piece, especially for the price. That being said, the fit, finish, blade grind, and overall quality on the Pro Series outranks the SG2 model.
The blade is thicker and more robust on the Pro Series model. I feel as though I could put the PS JYD to some hard use while I would only leave light and medium duty to the SG2 model. I also prefer the anodized Ti standoffs on the PS model over the single G-10(?) backspacer of the SG2 model.
If you got a good price on the knife you have and you're happy with it, then there is probably no reason to get the PS model. I know that STR charges about $40 for the tip up conversion. As far as IKBS being added to the Kershaw model, I'm don't know how much something like that costs. I know that Brad Southard has added IKBS to at least a couple of the Kershaw SG2 models, but I don't know how much he charges.
I'd like to see some pictures of the SG2 model you have. I saw one for sale with the IKBS added to it and I was going to pull the trigger, but decided not to for specific reasons.
The SG2 model by Kershaw is awesome and I can only see it being improved by adding an STR clip and an IKBS system. I've got two and they both have tip up deep pocket conversions done by STR. Maybe I'll send one to Brad for an IKBS conversion as well.
Pics, pics, pics!