Fastest PC

[scofthe7seas]

Any one of the low end Core2 based chips kicks the crap out of a P4.  Plus they can run a 64-bit OS with 64-bit MAME for a 15-30% increase in performance in most games.775 65W Dual-Core Desktop Processor BX80571E3400

(multiple responses to your post, but I don't like quoteing an entire big block)

Your recommendations are suspiciously close to my recommendations However, the pricing is a littttle bit off. It's easy to forget things like power supplies, and hard drives, plus if you don't have a space CD/dvd drive you will need one of those (at least for some of the initial work)
Also, you won't need 4 gigs of Ram, I rock 2 gigs in my mame PC on windows 7 64 with no hicups. There isn't really too much in MAME that needs that much ram (think about the sizes of the individual games/CHD images.. not so huge, and only one loads at a time.)
Also, Core2duo based processors are very fast, and honestly don't need much overclocking for mame. I haven't overclocked my ram at all, and often the voltage settings have to be meddled with which a lot of people aren't comfortable with.
The heating in any of the corex cpus is actually comparatively low. Look up some heating in alevels for a pentium D, you'll be pretty shocked. The low heat levels of the corx processors make them VERY overclock friendly. My mame pc isn't overclocked at all, but My personal one is. You can overclock to a decent degree just using the standard garbage intel sync/fan but I have a crazy looking zalman that keeps it very cool.
As had been said, it's really the emulation that needs to catch up (not at all knocking the amazing state it is already in!!) The 64bit issue is a HUGE help though, bringing NFL blitz from kind of choppy to very playable.

[JODY]

I say "Yes".  Get the Intel Core I7 and match it with very high speed RAM.  Install 64 bit Windows 7.  Use a 64 bit version of Mame.  Any it won't do at 100% is due to poor emulation.

My 3.4 Ghz AMD quad core (non-overclocked) can do the games I noticed glancing through this thread at over 100% and it is slow compared to an Intel Core I7.

64 bit OS and Mame yields a substancial speed improvement.

[scofthe7seas]

Seriously though, how many "high end" games are there that tax people's systems pretty heavily? Under 10? I don't know if that's worth several hundred more dollars. I loves me some games and all, but I'm made of bones and meat and stuff, not money.

[Donkbaca]

 +1 If you can play 90% of the games for dirt cheap, is NFL blitz really worth spending 300 bucks to play?