5.1 Digital Question

Hey all, I'm planning to get my 360 in a week or two, and had a question:

 I dont have an HDTV, but I got a 27" flatscreen, woo 480I FTL?  (hold your mockeries please.), but I have a wicked 5.1 surround system goin' on.  I have a digital coaxial input on my reciever, does this provide the 5.1 on the 360?  What cables would I have to get, and can I get a sound cable without getting the HDTV cables?  Is there an input on the back of the 360 for the big-ass Subwoofer cable? 

I just wanna make sure I can get my 5.1 surround before I get this, to avoid headaches.  Any sound nerds out there like me, help me out!  Thanks guys,

Well, you could get aOptical Toslink to Coaxial (RCA) Digital Audio Converter from monoprice.com.

You would need one coax cable and one optical cable. However, I haven't tested it myself, so I don't know how much quality you'd be losing through it.