Well, the DS is suppose to bo a portable console... Now, with this, you can't really use it as a portable system...
Nothing says that the amp isn't battery powered with rechargeable batteries like the DS itself. It probably isn't but it could be, Fender made a little can amp that worked that way. As for me, I'd just hook it up to my 30 watt amp that I already own. All it would need is a 1/8"->1/4" adapter that sells at RadioShack for around a buck.