Didn't see this thread so couldn't contribute anything but this layout of my setup might help others see the possibilities of a home network
I had the same problems of sharing music, video etc. Have three desktops, assorted wi-fi devices (iPhones, P1i, Archos PMP, PSP), Mediagate Network player and the odd laptops that my friends bring over.
Now I have all music, videos and essential software on a NAS running 2 750gb disks in RAID1. rTorrent on the NAS takes care of the downloads. Printer is also shared thru the NAS. Media server on the NAS helps me stream music/ video to the Archos/ Mediagate.
The Linksys WRT600N takes care of the wired giga lan (2 PCs+NAS+Mediagate ) and I use the 5Ghz band to connect the only PC on WiFi N. The 2.4 Ghz is used for all other WiFi G devices. DHCP with reserved IPs help in port forwarding and the like while not complicating any new additions to the network (for e.g. a friend's lappy or PMP).
The advantages of using a NAS are many. For one, if anything goes wrong, a hardware reset (mostly) is all I need to get everything back online. An average of 27 watts helps in keeping the bills down. Plus, power cuts are very frequent here. The low consumption of the NAS helps me in keeping the NAS+ WiFi Router+modem online thru power cuts of upto an hour (tested) on a generic 600va UPS
hyeah: ! Helps in getting that torrent downloaded real fast
hyeah: !Network printer sharing and the media server are like the icing on a cake. Only hassle is if I need more storage for shared file, I'll have to swap it out from the NAS. Works out better for me than a download rig.
The minus? It's way more expensive than a properly configured dl rig. But if one doesn't need giga lan speeds, there's a very good Thecus NAS (N299) going for arnd 10k without the HDDs. It's got 10/100/1000 in the specs but it's way too underpowered for giga through-put