So I finished the build. Was easy as..uh.. Pie
But anyways, I ended up using the raspiaudio DAC hat with the built in speakers. This stuck out a bit further then the small cover could handle, but lucky for me I also bought the larger cover for the back too, so no probs.
With the added depth of the bigger cover, I might later on.. use some bigger speakers in it, and perhaps mount a cooling solution onto the Pie's CPU. Thinking I'll need a pin extender ribbon, will look around for one, I'm sure they probably make them.
Another thing I did, was bought a new power supply that supplies a little more amps then the official one does. This is because I am powering both a Pie and the screen, along with whatever draw the Raspiaudio DAC needs. I also got an adapter that let me put a power button on the power supply, this way I won't have to worry about wearing out the jack, or unplugging it from the outlet.
I know when many people make arcades with a Pie, they'll usually load it up with tons of systems, but not me.. I'm old, I like old school, so this one is loaded only with Atari 2600, Atari 5200, Odyssey2, GBA, NES, Genesis, SNES, and a little over a thousand MAME games. In addition to that, I also enabled Pixel/LDME so that it can be used for casual net surfing. All that on a 32gb micro-SD, and I still have about 10 gigs to spare.
Also picked up a Rii mini wireless keyboard and touchpad. Very useful for emulators like the 5200 or Odyssey2.
Altogether, it cost roughly $200 to make when all was said and done. Here are some pics of what it looks like.