Depending on how you plan to use Herolab the laptop/notebook might be best for you. As for the kindle Dx I would go for an Ipad instead. I have both and the Ipad is great for gaming. I create or update my character in hero lab and put it out on dropbox in pdf format. Since I'm playing a barbarian I created two pdfs one regular and another with rage set to yes. that way I can switch between the two when he rages. That way I don't have to recalculate stats, attacks, hit points etc.
With the Ipad you get great battery life, various apps, email, and the internet.
I have been gaming with my ipad since October of last year and haven't regreted it one bit.
With pathfinder in mind. I can load the core book and any other books they have in pdf into Dropbox. Then load it directly into the Goodreader app( great app for pdfs). I can load a pathfinder character sheet from herolab the same way. If i want a dice roller i have my choice of apps to choose from. There is also two pathfinder related apps out there, Animal companion, and Summoner.
Now if your group uses Maptools, there is an app called Mapnakotic which lets me log into Maptools as a player. Its a free app by the way.
Basicly I can play with just bringing my Ipad with me.