my Pop'n Music add on to my MAME machine is coming together soon. I just ordered:
Flip-top PS2 import/cd-r mod
Popn Music 9
PS2 VGA Convertor
http://www.lik-sang.com/info.php?category=0&products_id=3235& (for those interested in which one)
Wico Dome pushbuttons
hacked PS controller
the buttons will be mounted on a swappable panel, identical to my current one with the capcom joystick/buttons layout. connect using the hacked controller, connect the PS2 to my 20 inch computer monitor
now its just waiting for shipments... and im very impatient

but i paid for extra shipping on the import items coming from HK, so it should only be a couple days.
ill be sure to take pics and let everyone know how everything works, i know a lot of people were thinking about doing this