A few questions regarding microSD cards

[TimeWyrm]

Or, should that be microSDHC cards.

I'm thinking of buying a 16gb microSDHC card, but I'm finding it really hard to find a reputable store that has cards that are class 6 (apart from dabs, but they don't know when they'll be receiving more stock). I want to get either a Kingston card, or a Transcend card. Does anyone have any ideas of where to get hold of one from (not wanting to spend over £55 inc del.)

Also, I understand the difference between class 2,4 and 6, (in terms of minimum write speed), but my question is whether there is a lot of difference between them in terms of playback of films etc. I'm not worried about how long it will take to transfer data to and from the card, just that I get the smoothest possible playback etc. I will be using it on a wm 6.5 device, and I be storing ebooks, comics etc on it also.

TIA