If you like tweaking with your router,
I warmly suggest you the ASUS WL-500gp (if possible the release 1 (not sold anymore), instead of the V2 version): you will find LOTS of documentation/firmware/...
I "upgraded" its internal RAM to 128MB (original 32MB), so I can run flawlessly eMule or Bittorrent clients without requiring my PC turned on 24/24.
By the way, attached to it there is also an HDD to save the received data...
Just some links:
http://www.dd-wrt.com/wiki/index.php/WL500G_Premium_v2http://wiki.openwrt.org/oldwiki/openwrtdocs/hardware/asus/wl500gpP.S. Please remember that you will need an external ADSL modem (this one is a ROUTER, not an ADSL/Router).