Psychofunk,
You in fact have it figure well, you'll gain the full single pass advantage of the greater number of tubes & no reversal of direction in the lower tank.
I would however only install a single outlet. The lower tank is one open run, so you don't need the second outlet & Y to rejoin your flow.
Edit:
Forgot to answer your other question. The "Stealthbox" system is FINALLY going to get built. It has been loooooooong delayed due to other demands on my funding that had to come first. I'm now try'n to decide if I want to go AMD 64 or Intel P4 3.4 @ ?(northwood). Costs of the 939 systems when released will decide which way I go, most likly AMD64. I'm VERY tempted to just build the P4 NOW, as I'm getting a bit parinoid about something else coming along to demand funding. But I'm going to keep my fingers crossed and wait. I hope SOMEBODDY comes accross with a good performing 939 board WITH pci & agp lock!