I would say it might be worth grouping them.
A fair few of the modellers I’ve encountered like an era.
So for example find all the WWII stuff then subdivide maybe by Allied, Germany, Japan, Russia. Then do bulk packs on eBay. Or do WWII or Cold War lucky dip packs.
I probably would get a list together first and then work the groupings out from there.
Anything that looks particularly unusual I might set aside and do a bit more research.
A basic Airfix 1:72 is about £10 at high street retail (Jet Provost bought a couple of weeks back as my measure) so you could do 10 kits for £70 or something like that, which ought to be more post and time efficient.
Edit of course I should have said there’s probably a few rare ones lurking in there but it’s really a question of added value vs. time of researching 550 kits to find them. Only you can make that choice based on your own commitments and inclination to get best value over freeing up space.