I think those Sample King DVDs can be useful for sure, but I never bought one. It really depends on the price though, most DVDs give you the info you can also find in the manual.. there aren't that many DVDs that actually reveal some work-flow secrets or work-arounds.. those are incredibly rare.

As for brands, there are a lot of brands that do work. There should be a thread on this forum somewhere where you can find brands that did not work. I'd recommend to at least avoid those at all costs.

You might be having a difficult time getting a hold on one of those 512MB card though.