You think I can get away with the cheapest CPU for my use?
Well, that's not quite what I was getting at.
MacGreen posted a link to a 60 in 1 board, which I don't think was what you had in mind. A 60 in 1 is basically a "hardwired" board that has, say, 60 game roms burned into it, plus a minimal front end of some sort. It's not a general purpose PC, so you can't really typically put your own apps on it (Maybe that is actually possible, but from what I understand, it's not typical).
When you mentioned wanting to run Hyperspin, that told me you were really more interested in a typical PC mobo/cpu type system, with a Harddrive stocked with an OS (Windows, if your wanting Hyperspin), emulators and roms.
As I understand it, Hyperspin can require pretty hefty CPU and graphics power to do all the slick graphics stuff it does. Mame generally doesn't need much CPU to emulate the older 80's/90's games.
If you want to run anything other than mame (same visual pinball or FuturePinball), then absolutely, you'll need a faster CPU and a decent GPU. Basically, anything that does 3d rendering. But mame doesn't do that, so it's not critical if Mame is the only thing you'll run.
I picked up an AMD Athlon Phenom II CPU/mobo combo several years back for something like 80$. It runs virtually all the mame stuff, Future Pin, Visual Pin, plus games like FoFix (Guitar hero clone) and StepMania (DDR clone) fantastic.