With that kind of budget and 5 machines you could get a well-rounded collection.

You already have a modern Stern..

Add to that: WOZ - there's nothing else like it

Then get a Gottlieb 70s-era EM like Card Whiz/Royal Flush, Jumping Jack

Add a vintage Bally solid state: Paragon, 8 Ball/delux, Supersonic, Strikes and Spares, 8 ball, Fathom, Flash Gordon, Centaur, Nitro Ground Shaker, etc.

Get a vintage Gottlieb SS: Genie, Black Hole, Haunted House, Mars God of War, etc.

And you have 5 games that represent some of the best pinball eras ever.

For example, a great collection: ACDC, Royal Flush, 8 Ball Deluxe, WOZ, Black Hole. No matter who comes over to your place, if they know anything about pinball, you'll have a game they'll flip out over..