If you already have Mame, I'd probably stick with that. But if you are hell bent on changing it up, maybe check into another multi board. 60-in1's are out as those are for vertical monitors, but the XXXX-in-1's are set up for horizonal monitors. And you get most, if not all, of the games from the 60-in-1's. If you decide to go for another multi, I'd say go for broke and get the 1940-in-1 or wait until the next release comes out with even more games. I've got a 1940 multi and have been pretty happy with it. Some games don't have that "true" classic feel, but with what you're already using, I don't think it would bother you. The only way to get that classic feel, is to own the original. If that's not an option, give a little to gain a lot I suppose.
The vertical games are strechted out a little, but it doesn't look bad, just looks bigger. And you'd have the options of having all of the Street Fighters, Mortal Kombats, Nintendo Vs. games, ect, ect.... to go along with the classics.