I agree that if you want to shop for other cables, you should take your MacBook and flat panel with you to the store and try it before you buy. But this requires the store to let you open the boxes and plug in your tv.
I bought mine at Best Buy. I've always had good experiences there so I didnt bring my flat panel to the store when I went to buy the cables.
However, when I got the cables home and tried them, they didnt work. I had to take them back and get a refund.
Then I consulted their Geek Squad experts and left the store with a second set of cables.
Again, I had to bring them back for a refund (to wit: waiting on lines again).
Finally I brought my flat panel to the store and persuaded the manager of the Geek Squad to open the boxes and test the cables before I bought them.
As I said, these are the cables that finally worked for me.