One thing that would be a good idea to keep in mind when looking for a bargain is your intended use for the SD cards, you don't really need a top end class 6 card for a lot of things.
SDHC cards vary a lot in their write performance and access time, and even the read performance for cards within the same speed class isn't as uniform as you would expect.
But in a way this is good news, as you can tailor your card for what you're planning to do with it
Say for the Pandora if you wanted to run another OS (i.e. Gentoo) then you'd be wanting a card with good read/write performance and crucially a good access time too (and of course a card that could handle multiple simultaneous IO requests well), however if you just wanted a card to put audio/video/ROMs onto for playback you really don't need much more than the basic 2Mb/sec read performance that a cheap class 2 card would give.
I've got a couple of 16GB Lexar pro cards that I'm planning to use for OS and tools, and I'll pick up cheap 32GB card for music/video etc when the Pandora is a bit closer
.
There was a link posted on here earlier for a high end (for the time) SDHC comparison review on Tom's hardware, that review was interesting as it clearly showed the differences in cards that on the surface are similar (due to their SDHC class) check it out
CODE
http://www.tomshardware.co.uk/sdhc-memory-card,review-31516.html