http://www.avforums.com/forums/showthread.php?t=376835
check that thread (warning it's long, so i suggest look from the most recent page first)
you will find links to CASH v1.1 and other stuff, and if you look at some of the other posted sites for reference to xbmc, on the front page of one of them if you scroll down you may find details of an FTP site, there was mention of them changing isp and thus opening up the ftp for a few days before the old isp close them down. they had loads of stuff like AID3, slayers disc etc, basically everything you could want
i haven't modded mine yet as i'm waiting on my xploder kit to turn up, but reading up on things it seems the folks on the forums here think CASH is the best install kit, whereas elsewhere people seem to think it's AID3
if you box is already modded and you just want to upgrade, i'd read up a bit more before you use install discs as it might not give the required effect. i get the impression to upgrade from one thing to another, you need to delete the old software first, then add the new, and ftp is the way to go rather than an install kit. i could be wrong however, i've just been reading all the install guides in prep for modding myself, and i got all the different builds and stuff so i could install the best version, but CASH was recommended to me