Hello!
I can speak from experience that the IPAC does, in fact, have enough power to drive the Atari cone LEDs. In fact, the IPAC provides TOO much power.
Look at the diagram at the below link under "HEADER PLUG AND LED WIRING DIAGRAM"
http://www.ultimarc.com/ipac2.html
As you can see, all you have to do is connect 220 ohm 1/4 watt resistors to each of the LEDs and the illumination is absolutely perfect.
Now, you may have some difficulty finding 220 ohm resistors... I know I did. I used a combination of resistors in parallel to get the 220 ohms. Unfortunately, I can't recall the values off the top of my head. I'll get back to you on that.... or maybe Warren_O could refresh my memory.
For the connector, you can use a "motherboard to serial port" ribbon cable off an old PC. Just cut the ribbon cable on the serial port side and strip the wires.
I see absolutely zero difference between the original annunciator board and my Daphne setup and am very pleased with this hack.
Thanks,
Brad O. "Please install 220 HOMES resistors. Thanks, bubby!"