I was in a very similar position many years ago, my first pin being lotr and my second being afm... I now also have st prem (along with woz, sm, and gotle). Afm is an awesome game, approachable for the novice, fast, fun, and deservedly a classic. However, in a small collection of two pins, and to complement your lotr, I think st is more dynamic, deeper game, with more staying power and a third flipper to change things up a bit. Theme integration is great in st (if you're into the star trek thing, especially the new movies), perhaps only surpassed by lotr and ij. It's truly a fantastic pin and currently both mine and my wife's favorite, but definitely not as approachable for the novice (starting modes is tough - aside from the freebie at ball start - and there's a lot going on). I'd go with st as the next purchase (plus you can get one nib, and finding a mint afm is tough and likely more expensive)