Or use IdeFix 
Since Maprom on the ACA cards adds so much performance it's really a no brainer to put update modules inside, I don't see how using IDEfix would be better? Unless the OP has a 4way IDE device and is using CD/etc.
@XDelusion,
There are some guides around for building your own custom Roms, using the maprom fuction it's self is dead easy, it's just a case of adding the following declaration to the first line of your startup sequence:
c:acatune -maprom devs:ks31.rom >NIL:
This assumes ACATune is installed in sys:c/ and your Rom image
(called ks31.rom) is in sys:devs/
See mfilos' guide here at Amibay about making custom Roms:
http://www.amibay.com/showthread.php?t=11935