If you're lining a Sage RP 7100, you have a fast action 7 wt rod. That rod will throw a lot of things, but if it were me I'd stick mainly to 7 wt lines, maybe an 8 for certain things. If you want to do "everything" with one line, you're screwed. It doesn't work that way.

How many spools do you have for the Hardy? And which model and size Hardy? If you only have one spool, then more than one line is kinda' pointless.

That rod is a good length and line weight for summer and fall steelheading. It's a bit heavy and overkill for SRC and trout fishing in lakes IMO, but it would certainly work. You can maximize the versatility of the rod with a Versa-tip line. Several brands offer multi-tip lines. They usually come with a floating, intermediate (slow sinking), fast sinking, and extra-fast sinking tip, 15' in length. I've never bought one, but I've been making my own since 1977.

As for brand, most of them are good, and you don't need the most expensive top-of-the-line line to have good results. Actually, Orvis is having a sale on some good Wonderlines right now ($29 for $65 lines) via mail order and Web. I just bought 3 6 wts, and I've bought others when they were on sale too.

If you don't know your Rocket Taper from a shooting head, I suggest you start with a WF7F (weight forward 7 floating) line or a 7 wt multi-tip, but those run well over $100 (probably why I still make my own).

Oh, and put some backing on the reel under the fly line (usually 20# dacron). How much depends on the size of the reel spool and of the fly line.

Good luck. It sorta' looks like you might need it.

Sg