If I had $5k laying around, I would buy either a GOTG or BK3 pro. If I didn't have any pins already, I would pick the Stern pro that interests me most (or one of the undervalued LEs, X-Men especially which is one of the best bangs for the buck available now). Metallica is a great choice if you like the theme and gameplay. Other greats that pop into mind are Star Trek, Spiderman, Game of Thrones, Deadpool, Star Wars (though this one is polarizing).
The idea of two lower end pins makes sense, but for me personally, there are no two ~$2500 games anymore that interest me more than any of the above Sterns.