I just read something that made me think of this thread.
 
It was on a photography forum, but was originally from a watch collector.  They said, "When you have one watch, you always know what time it is.  When you have more than one, you're never sure."

while all the suggestions are great I tend to disagree on some..
It's not always the price you pay that makes a good product, such as line..  There are so many out there that it becomes a matter of choice not so much price.. As said, my $30.00 sage line performs way better then the more expensive Wulff line..
I love nothing more then casting big streamers to salmon & steelhead..
Salmon streamers such as comets are slightly weighted (bead eyes or lead wrap ) with out having to add any weight to the tippet..
Most my steelhead streamers are not and thus I may weight the tippet..
The extra 6" is awesome as I only wade fish and is great for 1 handed spey casting..  My 8wt rods for salmon are 9'6" and cast much different then the extra 6" on the 7wt.. Possibly because they are different mfg's or the extra 6" loads the tip better but to me I like the extra 6" while standing tight to the bank..
As for an 8wt. to heavy for bass, well I said it was a bit over kill, not to heavy.. Heck I can catch sunnies on a 8 wt all day long but it's not much fun..
A 7wt. will cast big bushy deer hair flies just fine, they are light but very wind resistant.. If anything, like I suggested, go 1 line wt up on the rod, not up 1 rod wt..
 
All good stuff and everyone has their favorites..