i haven't been taxing my setup that much, but i do have it reading audio from a solid state harddrive connected to the hub, as well as the dac. i think you could be ok with the obd-ii and the dac. the one concern is that it states that it won't play well with all of the audio devices out there. i think they are talking more about soundcards that do a lot of software processing.
i love that minidsp, that is so cool. wish they had that when i was doing my corvette install
my initial impressions with the setup ive been testing is awesome. everything is working great together and setup was very simple.
you can hook up to 15 devices to the hub too.
I set up my router by just plugging it in. and attaching it to the hub. the belkin software did everything. the hub i am using is a linksys router that an old coworker set up in adhoc mode for another project. but i dont think that was necessary.
if i were to do it again, i would possibly look into getting a smaller wireless hub, but it's not a deal breaker by any means. As far as hooking it up to 12vdc. the belkin unit is a 5v@4amp device. i plan on just using an old m1-atx as a power supply for the router and hub so factor that in to you budget