I suggest you read through the
FAQ and look through Project Announcements so you can start to narrow down what you want your build to have and ask more specific questions.
So i'm building a new cabinet which I want an exit emulator button, an exit frontend button, along with 6 control buttons and 8 way joystick for player 1 and 2.Also 1 and 2 player start buttons, coin door, and room for whatever else I want to control.
1 or 2 inputs - Exit emulator button / Exit frontend button - Not sure you need both. Is this going to be a dedicated cab or standalone controller that plugs into a PC?
20 inputs - 8 way joystick (4 inputs) + 6 player buttons (6 inputs) for player 1 and 2
2 inputs - Start buttons for players 1 and 2
2 inputs - Coin door (2-slot)
So far, that's 25-26 digital inputs.
"room for whatever else I want to control" -

This makes it impossible to answer without reading your mind.

Check out this part of the
FAQ to add up your desired controls/input types/number of inputs required/encoders.
Do you also want a Pause button?
I want the buttons to be LED lit also.
Single color
or RGB? Single color always-on
or adjustable-color/brightness/animated?
Single color always-on LEDs are MUCH easier to wire than animated RGB buttons.
A long story short I want my kids to be able to easily navigate the frontend and know what buttons do what function. The arcade I have now they get in an emulator and don't know how to exit the game without help.
Dedicated admin buttons and proper software configuration will make this easier for them.
You can configure all your emulators and Front End to use the same exit button
Another issue is when I play racing games the key emulator doesn't work as well as a gamepad.The questions I have are:
Are you talking about racing games in MAME or console emulators?
Do I need an Ipac 2 because it says it is the only one that holds memory, or will any interface do that?
IIRC most encoders will hold custom settings without needing to reload other than the KeyWiz, X-Arcade, and
I-Pac VE.
Do I need an analog or a digital interface?
Depends on the controls you use.
Digital - anything with a microswitch
Optical - trackball/spinner
Analog - 270 degree steering wheel, SW yoke, analog stick
Do I need a separate controller like led wiz to control the leds,marquee lights, and etc?
The controller is for controlling the color (on RGB buttons) and brightness of LEDs.
Marquee lights are usually constant-on.
Do I need a separate switchable power supply?
Depends on the number and current draw of your LEDs.

Does it matter where or what kind of buttons I get, for instance do I buy off ebay, or buy from someone like ultimarc or groovy game gear?
You're definitely safe buying from Ultimarc, GGG, or Paradise Arcade.
Does the ipac or keywiz or whatever kind of interface control the coin door?
Yes -- the coin door is electrically just like an LED button. There's a microswitch that the falling coin triggers and a separate lighting circuit.
Scott