I just got a used XBox classic from Chris Pirillo and wanted to hook it up to my new Sony High Definition TV (HDTV) (got the 50" SXRD, but more on that on a later post).
The original Microsoft HD Kit is very hard to find (try eBay if you really want one) and I couldn't find info on what connectors it supported for audio (it supports component RCA cables for video). So I passed on the few that I saw on eBay and got the Monstercable Gamelink 400 X instead. Instead of being sort of a breakout box like the Microsoft unit that required additional cables, the Gamelink is a cable bundle, in other words one end plugs into the A/V port on the back of the XBox and the other end has the three component RCA plugs plus the left and right RCA audio plugs.
If you want to output digital audio from your XBox, the Gamelink 400 X also has a miniplug built into it which you then plug in the Lightwave 100 X Fiber Optic Audio cable from Monstercable. So instead of using the left and right RCA audio plugs you'd use the Lightwave 100 X Toslink connector optical audio cable for audio.
One major complaint about the Monster Gamelink 400 X though. The connectors they use for RCA are obnoxiously hard to get onto female RCA connectors like on your TV and such. They should move to a better connector type such as that used by Canare which slides on and off nice and easy while still nicely gripping the female connector.
I actually had to use a small screwdriver to open up the "fingers" of the Gamelink 400 X connectors so they would slide on a bit easier.
Be careful when doing this, however, as you don't want to make them too loose, but it's necessary for most users. As tight as the connectors are originally, you can actually take off the outer part of the female RCA connector.
Anyhow, if you are new to the world of the XBox classic or just got an HDTV and want to connect the XBox to it, it looks like the Monster Gamelink 400 X is pretty much the best way to go. Just remember to loosen up the gripping "fingers" on the RCA connectors just a bit though otherwise you'll have problems getting the connectors on and off the female jacks on your TV or AV receiver/preamp.