Flash cards options for the DS ?

I did some research and read some of the topics here, it's seems that the Supercard miniSD + SuperKey is the best package to buy so far, but iam a bit worried about the slowdown issues on some of the GBA backups and the quality of movies\MP3 after converting.
Is there any satisfied supercards owners that could enlighten me about the GBA compatibility issues ?

Iam also looking for a trustworthy online store that sells these cards at a good price.

I owned SC and I concur that GBA compatibility isn't the greatest but it runs DS games smoothly.

I'm thinking of getting a new flash cart and I'm leaning to G6 Lite.

A good place to buy online is jandaman.com.