I was in your situation when I started too, spend my entire budget on 1 NIB Stern or buy a couple games. Canadian pricing for NIB is pretty high ($7700+13% taxes from the dealers here). For around $1.5k less than that I got a pair of games (Jurassic Park and Getaway).
With the current market, even if you get bored of your games, you can sell them at break even a few months down the road or trade them for something else.
If you have the space I think getting a pair of used games will give you a bit more lasting power vs 1 Stern, plus then you and your wife can play at the same time.
If you can only have one though, I'd probably buy a deep rule set Stern. I played Ghostbusters for a solid week when we had it at work and it is a hard game with the flipper gap and the Scoleri brothers pop ups. Deadpool looks good though.