To the extent that a novice may give advice to a neophyte, it would be this: "Increase the budget: you've earned it!"
In all seriousness, this is a very big occasion and a very significant purchase. It's not unreasonable, is it, to allow yourself (say) a grand for each year of the fifty? You're clearly no fool; you clearly have an interest in watches; you obviously have firm ideas about what you want and like. The 'spend' is in good hands.
Otherwise, the advice you have been offered by others here is good advice. You may wish also to have a glance at the Independents; it's a personal vice, but there is something somehow apt in having a limited or bespoke piece as the mark of a significant occasion.
Much more importantly: thank you for gracing the forum, and welcome. Hopefully we will see a lot more of your thoughtful contribution.
Cheers,
pplater.