The duct would of worked ok if you attached that to the bottom of the two rear fans and then had the top fan sucking that air straight back out again.
What have you got in the top 5 1/2" bay ? can you not bump the other drives up.
Do you ever use the floppy drive ? might be worth removing it if its not used that much.
From the stickers on the front i see the case has done you well, what with the original pentium sticker on there (pre mmx!) perhaps a new case is in order they are still cheap these days for a real basic one.
As for your graphics card, is that a heat piped passive cooler on it ? if so you would be much better off cooling the heat exchanger on the back than the front of the card like that.
Edit - £11 ...
http://www.ebuyer.com/UK/product/108279 also avaliable in black, has space for a fan on the side panel though i think it will be to far back for your mobo. It has lots of hard drive slots which you seem to need ..
For a few extra squid you can get frills like front usb ports. Its only 39cm long tho! They do a 44.5cm long one which will give you more room. They do have alot of colours styles etc all for around the £20 mark.
However this is the case to die for, i still havent worked out how your supposed to get at your rom drives but still ... it will solve all your thermal problems!
http://www.thermaltake.com/product/C.../vd4000swa.asp Its only £180 but includes a full water cooling system. Its alu so the case itself is light, however the whole lot would be heavy due to the litre or so of water required.