It depends on how much you want to get into doing some of it yourself. The kits that Sherline and the many others sell are nothing particularly special, and in fact can even somewhat underperform a package you assemble yourself. In any case they usually cost a couple of hundred dollars more than the parts that make them up, parts you can just buy directly if you desire.
If you are at all familiar with even the rudiments of basic electrical and electronic work you should not be worried about the technical aspects of assembling your own kit. It's pretty straightforward. It should be primarily just a value judgement as to whether or not the hours saved and the peace of mind to have someone else pre-assemble your setup outweighs the extra cost, or perhaps of you just having a desire to do it yourself.
After that it is a question of budget and desired performance.
After you have made those two decisions we can suggest options to best fit, there are a lot of them.
BTW, I'm a jeweler as well, and you won't regret going CNC. It changes the way you will look at the business, your designs, everything in fact. Just get damned good software, its the best investment you can make by far. Artcam, 3Design, Matrix, etc. The cheaper stuff just doesn't cut it, costs you a lot more money and grief in the end, just like bad bench tools do.