I would make a couple suggestions.
I would not put a floppy in a HTPC, it will look like crap, and when would you use it. You won't even need it to install the SATA drives as MCE 2005 comes with SP2 installed.
My other suggestion would be noise levels. I would go for as silent as possible. The stock HSP on the P4's is loud, and so are most vid card fans, and PSU's of course. I would spend some upgrades on "silent parts." It being in the living room and everthing you definately don't want it humming too loud. They even make fanless PSU's, but they're kind of expensive. There are a lot of sites out there but here
is an example.