For a complex game to sit next to your FT I would pick Whitewater, one of the most complex rulesets ever, the most ramps ever, and the best topper ever, great all round package.
TAF is grossly overated, that does not mean it is a bad game, but it gets big $$$ because of the reasons mentioned above, everyone can remember playing it.
ST:TNG is a great game with a deep rule set
TZ is a fantastic game with so many toys from a time when pinball had huge budgets, Pat coming off the sucess of TAF threw everything into the game.  The rules are not complex, light all the door 6 ball multiball, its just getting to know what to do in each mode that is tricky if you haven't played it much before.

Bang for buck is the WH20
Unlimited budget TZ
Theme that you guys are into ST:TNG

End of the day you cant go wrong with any of the titles you have mentioned