First, most lines sold in the US "over test". In other words, they're stronger than the label says they are. So, your 6# line is probably closer to 8# or 9# line.

As for the medium rod and 12# fluoro, I think it's overkill for crappie. Yes, fluoro is less visible, but the thicker line affects how your bait acts in the water.

You might try a light rod, but I wouldn't go over 6# line. (I use nothing but 4#, myself.)