Ok, I'll bite.

when chaining 2 firepods, do you have to run from the CR outs on the second unit as well to hear those tracks?

No you set up your monitor outputs and all audio will be heard from there. It is similar to buses on a console with the exception that you can actually assign your stereo pair to any output you prefer to use as the main out. There are what 8 outs at the back of the firepod? This is so that you can assign each track in Nuendo to a corresponding output so that you can use a hardware mixer and effects in an actual reality kind of way as opposed to the virtual mixer/fx in Nuendo.

2nd question: what's the best way to monitor my final mix? Would I still need to use the Firepods, or can I just go out from the audio ports on my PC

Why would you want to do that? Why take the decent sound your getting via the Firepods and route them through the crappy on board sound card that you have or Soundblaster for that matter?

I've got 8.1 capability on my PC

You also have 8.1 capabilty in Nuendo and via the firepods. It's just a matter of making the investment for decent monitors.

US2400, I'd like to be able to see all 24 tracks without having to budget for another Firepod.

The tracks you "see" on the US 2400 are virtual. There is no actual routing of the Firepods outs to the US-2400. it is merely a control surface. If you need the actual outputs routed to a mixer, you will need to spend a bit of money.

Thanks for taking me up on stupid questions (no such thing as them, right?).

I realize now in retrospect that I'm simply over-thinking my build. :oops:

But thanks again! I really do appreciate the advice.