[Hampshire] What is a Shuttle PC?

Hi all

I've done a bit of googling but (apart from the obvious shape of the case) what's so special about a shuttle PC?

I'm looking to put together a new machine with quite a bit of grunt (6Gb RAM+ and as fast a CPU as I can afford). The only other real specification I need is that it can handle dual monitors. Aside from that, standard sound is ok, as is standard network. A front USB port would be handy but no other major requirements. I intend to dual boot Ubuntu and Vista and the main thrust of the machine's work will be video editing (hence the RAM, CPU and graphics).

Physical space is an issue but is there anything else to watch out for? I notice for instance that lots of Shuttle PCs have only 275W power supplies - presumably the case can't take any more hardware so a stronger PSU isn't an issue - is that right?

TIA - I promise I have done a lot of googling on this but not turned up the one answer I need - why buy a shuttle PC as opposed to a traditional tower?

Cheers
Rob