Bill acceptors are a must, no doubt. I would suggest you keep an eye on both your top and bottom line. Unless you have an "A" location, you probably won't need a Mars acceptor. Nothing against the Mars as I have some of those too, just that it--rightfully so, is much more expensive than the Pyramid. I have used the Pyramid Apex 5400-U52-US and it works fine in newer Stern, can't speak for B/W. If you end up going with the Mars, Lloyd's advice is spot on in going with a rebuilt unit.
If you end up placing several or more games in one location, consider a change machine instead of acceptors on each game.