I have z5500, I can tell you they are great speakers
Regarding your question, lets see what I will consider plus:
- Multiple line-in conections: connect the xbox, the pc, a dvd player an iPod all at once, no need to get up or disconnect cables, reconnect the other cables, etc
- Dolby and DTS decoder: view movies in your tv using them as a home theater (since you have xbox I assume you have a tv in same room to use it, also if xbox has dvd player fetures)
- remote control (usefull if tv/speakers will be far to reach or need to get up to use the volume)
- great sound quality
Hope this helps...