Suggestion for cheap/slow MB with 3 USB and can boot from memory card?

Hey guys,

I'm looking into building a classic gaming console, and I'd like to make it as cheap as possible, but to have the following on the MB:
* 3 USB ports (2 for controllers and one for keyboard)
* can boot from memory card (or some sort of easily removeable flash memory (I want to do that vs. hard drive because the goal is to be able to possibly have different cards for different emulators/boot OS's, potentially)
* no controller(s) needed for hard drive/floppy drive/CD
* either needs onboard video and audio capable of output to TV (A/V, S-Video, HDMI, etc.) and audio (phono) out or has 1-2 card slots of some sort (PCI, AGP, PCI express, etc.) for those purposes (and suggestions on cheap cards much appreciated!)
* x86 CPU support (preferably supports a CPU that is very cheap)
* memory requirements relatively small (not going to be running much on it)

I have seen micro-form factor stuff like gumstix and other various small-form factor PCs, but I was hoping to find something that was very cheap (aim is <$150 for the whole system, so MB would need to be pretty cheap) that just had the necessities above.

Any ideas/direction? Sorry if this sounds nuts.

Here is what I'm talking about:
http://www.linuxdevices.com/news/NS6372429785.html

The TU-40 is just a bit underpowered for emulation, although it would handle stuff for the most part. I need to see how much it would sell for these days...

I found some more stuff on the linuxdevices site (appears to be a good reference), including this Atom MB at what was $80 in January (2008) which includes the Atom 230 CPU which was $29 if purchased alone:
http://www.linuxdevices.com/news/NS6489450984.html
It had a whopping 8 USB along with stuff I don't need though, but it looks cool.

Also the Icop eBox-4300 looks neat (as a system) and that article refers to some more devices that might be of interest:
http://www.linuxdevices.com/articles/AT4708024578.html