First, hello to all - I'm radiator, a complete arcade building noobie

Just got some questions I need answering (that have probably already been answered before!)
I've been thinking of building a MAME/other emu cabinet for quite some time (2 years) but due to lack of money, kept putting it off.
I'm on the budget side, so the cheaper the better, and need advise on what to buy. I've decided on buttons/joysticks by Happ, as they always seem to get praise, and the I-PAC interface from Ultimarc.
I'm just kinda stuck as to what to get graphics card-wise.
I want the machine to be able to play many emulators (mainly MAME though - DOS version (unless anyone can give me good reasons to use the windows version)), and would like some kind of setup where I get a boot menu when the cabinet is switched on, giving me the choice of loading either a DOS emulator front-end, or, to boot into windows (which will be customised - ie, no 'classic' icons, hidden start menu etc, icons to each of the emulators).
I'm defintaly gonna be using a TV for the moment, as I can't really afford a decent sized PC monitor, or arcade monitor - I can probably pick up a 25" TV for around