Yeah, I don't know why they even make...oh. They make analog multi-syncs so they don't have to make three different kinds for dedicated games. So, yeah, what aholfe said. I wouldn't put a 27" for Mame in an old-style cab, anyway.
Use a PC monitor - though a PC monitor doing native resolutions doesn't mean it'll look like an arcade monitor. It just means that it will fill the screen (depending upon the orientation of the game and the emu orientation setting) without stretching the image. As aholfe mentioned, it's VERY crisp. No reason to use an avga with a PC monitor, as Mame does fine by itself. (As the PC monitor can't match refresh rate, the game behavior is irrelevant.)
Then, when you decide you want to go the whole route, make yourself a cab and CP and get a multi-sync.