I've purchased numerous DBZ cels from Anime Taro. 
They consistently get some of the highest quality 
cels I've seen available - at least on a regular 
basis. It's just a matter of timing, and being 
there when they update. Since the way their 
system works, the cels which have 
been "purchased" (or put into your shopping cart) 
disappear, you probably have just missed seeing 
them. Keep an eye on them and you'll find some 
really incredible cels, not to mention genga. ^_^ 

Good luck! :)

Sheri