@avlee
Im new school like you and like you bought my 2 x d8b's recently for the same reason...to use as a DAW controller. However, that was just the bonus...really I decided to do more Euro style mixing (analog console) so the d8b fit the bill. And I came across a "bargain deal" for mine as well.
Anyway, you dont need anything other than the mixer to use with Munk's ProBox and Marc's D8bridge. Its good that you have the cpu/psu & mixer...but you dont need it. Plans for a internal power supply will be posted soon. As far as those effect cards or audio cards..useless with DAW controller ONLY use. Both Probox & D8bridge DO NOT provide audio function. However, the Probox will do talkback and monitor but those will be thru the audio jacks, not thru cards...so again you dont need them.
So to answer your question, you're fine with that system as is. Just buy the Probox when it comes out and plug&play.
If your studio needs expand to where you need more I/o for mixing then the d8b come in handy as a complete system.
But if you never plan on coming out the box again and just want to use it as a daw controller only then find just the mixer. Those can be had for $100-$200.
But a bargain on the whole thing is hard to beat.