I think staying with the Jamis is a sensible idea ... of course, finances allowing, getting a new bike is always the BEST idea, but sometimes we slip a little ... no judgement. You can still buy a new bike later.
I figure any bike I have enjoyed for five or more years is worth very little, because most people are either looking for a new entry-level bike in the relative price range, or a super deal on some older bike ... and I am not rich enough to feel good about giving someone a super deal when I need the cash to buy my next great bike ..... Someone Might just fit my old bike, and like the specific upgrades I made, but likely not ....
if I had good gravel close by I would invest (possibly) in a gravel-specific frame with good tire clearance and all that ... otherwise, it is hard to imagine a road bike which would be So much better than what I have, that the price would seem justified. Like your Jamis, my bikes are unique and fit and suited to me ...
Let me string together a few years of several-thousand-mile riding (4K or more) and I will start talking myself into the big cash outlay ..... by then bikes will have 28-speed automatic gear boxes shifted by telepathy and micro-shocks and miniature heaters and AC units probably .....