Hi, I'm guessing you want it connected for the Sound rather than anything else. I'm not entirely sure what audio connections the Xbox has... optical?
well it depends on your TV, and if you have any other devices. You could use an S-Video cable for the DVD player to your TV if you have the connection then this will free up the Scart socket. This is what i use as i have it connected to the LCD which has no scart at all!
If you dont have this possibility you could use a VCR or something which has more than one scart (preferably 3) and piggy back them ie. TV-VCR, VCR -DVD, VCR- X-Box
Thats my only suggestions, there could be other ways.
I personally have a gamecube running off it, with just the Audio phono's going in to the AUX connection which gives me Dolby Pro-Logic II, i dont believe you would get Dolby Digital/DTS from just the Scart connection.