I think TAF will be too similar to FT. It does not have a deep ruleset, just complete the mansion - but it is not easy to do. ST TNG - complex ruleset second to TZ, but I think machines with "deep" ruelsets are not as playable as "fun" games like TAF.

TAF is similar also to Scared Stiff. I love both games. TZ is similar to ST TNG - deep rules but the gameplay suffers. You have to be either in the "fun mood" or the "serious pinball" mood. Get one of each and you have all bases covered. You have a FT, so I'd be looking more at a ST TNG than a TAF. $3500 for a nice ST TNG (good ramps and plastics - no wear) is a fair price.