Hi
>> I fomatted the complete 160 GB disk to ext3.
Good
>> After enabling the Samba via the web-configuration, I got the HDD mounted to /tmp/harddisk.
Normal
>> I read a lot about mounting it to /opt.
>> Does this make a difference?
No, /opt is for installing aditional software for the router, nothing to do with the file sharing stuff
>> And what about the read speed from a XBox (XMBC)?
Should be limited by usb port speed debending on your 500g model. Using ext3 on hd eliminates at least some samba poblems you get with fat32.
Greets
My Stuff: WL-500g, Mapower H31x 10GB HD, Philips Webcam Vesta PRO, TerraTec Webcam PRO, USB Hub