If you've got absolutely no clue about what bass you'd like next, then perhaps it isn't the time to buy a new one? If there's anything your current bass can't cope with, that would be something to focus on for a start.
You want to 'upgrade' your bass, but your budget is exactly the same as the price of your current bass. You need a versatile bass, which is exactly what a jazz bass is good at. If having a second bass is all you want, perhaps you should choose one that looks good?
If you are persistent of buying a new bass, you should try to find one that 'fills in' the gaps your other bass leaves. Or vice-versa, one which has gaps that can be filled in by your jazz.