<< They may pretty decent but for less money you can buy a pair of 100Mbps NIC's and CAT5 cable to roll your own. >>
Home PNA 2.0 kits are cheap as borscht these days. Not as fast as 100 Mbps Ethernet, but a helluva lot less hassle than rewiring your house. Speeds are supposedly comparable to 10 Mbps Ethernet or better speeds (ie. less than 10 Mbps) in real world usage. Not good enough for DVD, but probably good enough for Divx. MP3 is relatively low bandwidth though, so that's gonna work for sure. I use it for streaming MP3 myself, but like I said, MP3 isn't taxing it very hard.
My setup.
Cable --> router:
1) Router --> 802.11b wireless bridge --> laptop
2) Router --> 100 Mbps Ethernet --> desktop
3) Router --> HomePNA bridge --> telephone lines --> MP3 receiver
Everything works great, and the wireless and HomePNA bridges are transparent to the router, as expected.
I've also used HomePNA with DSL and voice/fax all on the same phone line, with no significant signal degradation of any of the above. HomePNA is great if drilling holes in your walls is not an option. More reliable and faster than wireless 802.11b too (although I wouldn't give up wireless for anything).