DIY trickle filtration

Hey guys, been doing some thinking about the possible layout of a filtration setup, to hopefully accomodate a 400L tank, or thereabouts...

I have either got a 2 food aquarium tank to work with, or can accept any other friendly suggestions...

I was reading on australian cichlid enthusiasts forums about using a bucket as a filter setup...

was thinking two 10L buckets (or larger, whatever is available) with a spinner arm (whatever u call it) at the top, and then say a layer of filterwool, before bioballs. then a 1" gap at the bottom, then drill a hole in the center of the bucket, mount some sort of hose connection, let that flow into a common sump (could use the 2 footer, or a plastic storage containter) with a powerhead in it to push the water back into the tank..

If i have approximately 8L of bioballs in each bucket (16L media total) is that enough for a 400L tank?

would a 2500L powerhead suffice?

Or is it just easier to stick to a conventional all in one sump style setup...?

Can anyone direct me in the way of some good reading material on DIY sumps, wet drys etc. i have already cheacked out http://www.csd.net/~cgadd/aqua/overflow.htm

any input is greatly appreciated.