RE: line weight to reel weight, any significance?
I would be hesitant about buying a 6 wt. for saltwater. There are two reasons behind this:
1) the fish you will probably catch in the salt will be too large for that weight rod and you'll have to tendency to fight the fish to exhaustion (which as we all know increases fish mortality). That's fine if you plan on keeping the fish, but most of the stripers you'll catch won't be keepers. So in effect you'll simply just be killing a bunch of future keepers. :);
2) Try casting anything more that a wooley bugger into the wind on that rod and you'll be selling that rod on Ebay the next day.
I wouldn't fish the NE salt with anything less than an 8 weight but a 9 is probably better all around (and a 10 is even better in the wind). As far as the line / reel wieght goes, as the other posters said, you'll harm your cast if you don't match the reel and the rod because the setup will be off balance. Honestly, I've never done it, but from my experience is just doesn't seem like a good idea.
I think we're all curious to know where you got the idea for the 6 weight in the salt (not to mention matching it with a reel made for a 9 weight rod). Whatever the source, if I were you, I would listen to the time-honored rule of flyfishing and match the rod to the reel (whatever weight you choose).