Are the I-Pac 2 interfaces a good choice?
Here's the link: http://www.ultimarc.com/ipac.html
I-Pac is good for push buttons and 4/8-way joysticks.
It won't work with spinners/trackballs.
There are a number of different options for encoders. (IPac, mini-pac, keywiz, KADE, ZD, Xin-Mo, . . . )
What controls are you planning on including on your panel?
Before you start buying parts, you may want to go through the design process like
here and read through the rest of the FAQ to see other considerations that you may find useful.
My second question is: Are they compatible with the MAME Software?
MAME accepts inputs from all of the various
encoder types: keyboard, gamepad, optical (spinner/trackball), analog (analog joystick / Star Wars yoke / 270 degree steering wheel / gas pedals), and rotary joystick. (ikari warriors)
Scott