If you do correction, Rupes or Flex, if you are just looking to amp up the gloss, the PC or Griots works more than well enough. The Rupes is definitely the smoothest and easiest to control.
Agree with Scott. If money isnt a concern, narrow your choice down to the rupes and flex and research from there. The Flex from what I've read (I don't have one so I can't say personally) is a little bit of a different animal to work with but there's plenty of people that like both. Google "flex vs. Rupes" and start reading
if you're just a weekend warrior and want an affordable and powerful DA with a good warranty then get the GG6. with microfiber pads (and many others) and the plethora of different polishes/compounds out these days, there really isn't much you can't tackle. if you can wait, HD is coming out with their own DA which will be hopefully be available soon...
The word is that Flex will unveil a new product at the SEMA show. I have no idea what it is but one would "assume" it would be something to compete with the long throw RO's like Rupes.