Yeha, I'm going to wait on the Pi2 until I can see what they can do with the new one. I know, ideally, I'd just scrounge up parts, but I just don't have much at the moment, apart from a couple HDD's. And I hate the thought of paying $400-$500 for a PC just for MAME. Heck, my main Dell 8300 XPS Desktop i7 was only $600 or so.
I'm not averse to building, but with family, work, etc, prebuild would be a nice head start, since I have to learn the MAME and other config stuff.