I'm in a similar situation. I live around 4000 km from the nearest decent stock of trumpets so trying is not feasible. I've bought a few horns online and, like you, my experience has been good. The Jupiter you are looking at is a fine professional model instrument. It will certainly feel more 'open' than your current trumpet but not just because of bore size. If the deal on offer is a spectacularly good one I'd say go for it. If it doesn't work out for you, you should be able to sell it on if there is such a dearth of quality instruments in your home town. Otherwise maybe wait a while.