Somebody told that for Xbox Live, ADSL of 128k could work, but I would havea chance of massive lag spikes. So would 200k be enough or what? 
they still offer speeds that low?? I would recommend the absolute bare minimum would have to be 512k
yea seriously if you tryin to play XBL on 200k thats liek playig every game made by Blizzard at once on a Dell