The PS3 does appear to support files stored on a USB drive (see this page for mention of this ability when playing back music), but I'm not familiar enough with it to know what file formats it works with. When you do this, though, I don't think there's any way to see the data from elsewhere on the network (short of moving the hard drive somewhere else) - so you wouldn't be able to store you music at the PS3 in this way and have that data available at your PC at the same time.

If you are remodeling and can add some wiring conveniently, I'd definitely suggest running some network cable to your entertainment center - I did that last year (thanks to the attic and one-story house) and have both an HD-A2 and a SoundBridge M500 on the network, making firmware updates for the HD-A2 painless and avoiding the need to ever worry about WiFi setup for the SoundBridge. With two more cable runs in place, I can add a PS3 and still have a free cable - and if I ever did need more network connectivity (can't imagine why I would now, but it's hard to tell what might crop up later), I could always stick a small network switch in the equipment rack.