Under Gravel Filter Intake

I'm building a new tank (100L / 25G) and am a complete novice to fish
(my girlfriend wants the fish, I want an engineering challange - the
fish'll be nice too).

After some reading about filters I thought that the best system would
be an external cannister filter with an under-gravel water intake
(several pipes with small holes). I also think that this would be the
most aesthetically pleasing, since I'll plumb it through the side of
the tank.

I have two questions:
1) Is this a good option?
2) How do I build a multi-stage (3 or 4) cannister filter? I have some
ideas but have seen no plans.