@ 4hannons, sorry for slow response. The Acopian model I happened across on eBay was A18H1400. That's a Gold Box Type A linear regulated supply rated at 14 amps output.
14 amps of current is somewhat more than the stock Mini power supply's output, which is nominally 10 amps. Message board posts seem to indicate 8.5 amps is quite sufficient. However it's best to keep in mind that some extra power is needed to feed the USB and Firewire buses, so if you power a drive or a DAC from the Mini, you will definitely need headroom.
Acopian model number A15H1150 is definitely big enough. This one is specified as a 15-volt supply; the idea is to require your unit be built to output 18 volts, when you place your order.
Acopian has been really great to deal with, in my experience.