22 CC's tubes! That's bonkers.
It's going to weight a tonne - would really incourage you to have them wall mounted or on stands with QC's
Tweeking a pc when you have rads on the side pannels is a nightmare (ask WJA)
And check the amps on the nightjars - I don't think they are man enough of a 5870
Fanless psu and high end gpu's are not friends - maybe with two it will work but I'm no electrical guru.
Just checked and it's 32amp (rated for 1x 4890 or 2x 4850) Nice
BUT the nightjar need case airflow (which my Jesico doesn't due to rear heatsink fins)
Also have a look at the Mcubed t-balancer for the fan/pump control - really usefull for low speed / non-stalling of fans.
I would also be tempted in looking at the Typhoon 3 - one pump two loops but have heard it makes the D5 louder...
as to galvanic corrison - you will need an inhiberiter but as you said there is nothing in direct contact (check the tube threads for damage) and your Al:Cu surface area is high so that helps too.
Having some airflow is the best approach - if you hadn't already got the nightjars I'd say use a quiet fan psu.
But now, just block up all the vents and have the fans as intakes with the air being pushed out via the nightjar(s)
Not trying to tell you how to suck eggs - and always good to see someones elses approach to passive watercooling
+1 sub
Edit: have you got any images of your last passive array - you had a water bar last time if I remember correctly and a corsair on the carpet.