My first Pro camera for Weddings was the 6mp D100, which, within certain obvious ISO limitations was fine - and cost me about £1,250 plus £250 for the 1gb card
My second was the 12mp D2Xs, which, within certain obvious ISO limitations was more than fine - and cost me £3,500
My next was the 12mp D300, which, at about £1,000 was better than my D2Xs
My next was the amazing 16mp D7000 costing around £700 and was better than the D300
My current 24mp D7200 is the cheapest I've bought so far at around £600 and if by FAR the best of the bunch to date
The D500 is FAR too expensive and too advanced in many ways for my needs, and easily able to shoot pretty much anything, in fact with modern tech being so good I could happily shoot on the cheapest current Nikon DSLR and get similar results
I am considering changing systems though and it'll either be to the Fuji XPro2 or the D750 - neither is fully 'Pro' spec cos Wedding togs just don't need cameras like the D4 - that's a waste of money
Oh and its ALWAYS 2 bodies that are the SAME, this is sooooooo much easier to shoot without having to allow for the differences between bodies and how their sensor's record, so I certainly wouldn't consider a D500 & D750 to be a good Wedding pairing
SUMMARY
Just in case you couldn't be arsed to read all of the above...
ANY modern mirrorless, FX, DX, camera is good enough for Weddings
Dave