The Yamaha QY70 and SU10 pair is my favorite portable workstations combo. While the QY providing a full sequencing strength with a reasonable XG engine and nice fx, the SU10 providing all the bits and slices of samples and loops to make things even more fun. Those puppies might thrown in some reasonably good material and some punchy samples. I even sometime view the SU10 as a poor's man SP12/1200 :O) Both run on batteries and portable enough to take anywhere.
Even Freezepop, prefer the QY70 over the QY100! haha..http://www.freezepop.com/gear/index.html