Yank out out everything underneath the divider (Cyprio, your not done yet, still one piece left
First thought that comes to mind: Do the bends like Marci said, make a duct to join PA160 to fan @ 90degrees and route the air out one of the sides (Barbs get in the way of the front). No matter what you need a barrier under the case (foam?) to keep a circular recirulation from forming (place it on the side where the fan exhausts).
You could try sealing the chamber and using that as a duct but that would require seals around tubing also.
I might seriously consider top-mounting (nearer the front). Or if you have the room in the back, just suspending the thing and running the tubing through 1-2 pci slots?
Oh, yeah, upside down it bad since its the one way bubbles have a REAL HARD TIME escaping.
/Edit 2: is teh spacing between rad (need 1/16" underneath to put SOME noise deadening/seals (weatherstrip) and the top of the bulkhead 120mm? Looks like the idea w/ the 2 side mounted fans (extension of my other thought) would fit w/ a custom duct w/o pulling the bulkhead (practice w/ cardboard first and DONT CUT THE CASE!!!! until you get a perfect fit). Fans would mount to (and be supported by) the outside of duct and then you just match up and cut holes in side (s) of case (is this going against a desk/wall, think b4 designing). Mount grills to case outside. and some more weatherstrip for inside seals/ shock killing, thus removing need to mount fans to sides of case! (Can remove sides on a whim instead of unscrewing stuff first

) I am going to do this w/ my system except I am using a 150mm Papst @ 5v

(Trying to find a PA160 in the states but not getting there Marci

, so will prolly use a 2-342 instead.)
And will fans go above lower / front inside case side support pieces (this is a MUST)
Out w/ teh front fan (blocked anyway) like in one of your lower pics. Also I am going to mount a spare drivebay assembly like you are thinking and stick a fan in front of it (If $$$ not problem, Get EX-34 from LianLi (EX-23 is another option) and you get extra air in the case also). Or take drive holder and place up 1/2 - 1" on its side so you can use the drives heat differential to set up cirulation between drives as hot air rises of drive. (haven't really thought about this to much

)