I have many light rods, because I think they're fun.
FWIW, as an all around rod, a 4wt is better than the lighter ones. If you already own a 5, maybe that's not enough of a drop? My 4wt 8' Versitex is damned near perfect for dry flies, wet flies, single light nymphs, and hopper dropper fishing. It is a perfect all around rod. You could probably build one of these for around your $100 price point.
Yet, I seek to replace it at every turn. It is also the benchmark.
I own the cheapest model LL Bean Quest 2. Its a 6'6" 3wt. With a 3DT lone taper line, its a bit to fast for me, but still highly accurate and very light landing. I also routinely fish it with a 4WFF line, and I find it slows it down and makes it easy to laser beam out a single fly. It is, however, too short for my general tastes. I think it was $70? After trying the new Ultra SL 9' 5wt, I'd be hard pressed to not try out their 3wt and 4wt rods.
I own a 7'6" Superfine 1wt. I love this rod, and used the hell out of it in the end of the summer, including the sole time I could be bothered to wake up for trico fishing. With the matched 1WFF Superfine Trout line, its accurate, fun, and it flexes to the bejesus which I find pleasing. Most people would probably find it to be to whippy and light. For anything other than a 14 dry and maybe a light dropper, its not gonna do you much good. Its also out of your price range, but I list it to help give you perspective.
I also own a 7'9" 3/4 McFarland glass rod. I'm still dialing in my feelings on this, but I do love the bend and action. I find that I'm struggling with really open loops on the long taper 4DT line I'm using, at least with multiple fly rigs. Trying a 4WFF GPX wasn't my style, it loaded too much for my pleasure, but did seem to exhibit the desire to stab rising fish in the eyeball with a size 16 fly, it was that accurate to me. Unfortuantly, wasn't a fan of the rod with that line otherwise, have yet to try a correct to AFTMA 4wt line on it, though. I picked this one up because of cosmetic damage for just outside your price range. Watching for used things might do you well here.
In the end, in my ever so humble opinion, I think an 8' 3 or 4 weight rod would be just about perfect. I'm willing to waffle by a half foot in either direction, however.
I'm a sucker for cheap. I wanted the 7'6" 3wt Three Forks, but my innate dislike of the Cabela's name on my toys turned me off (yes, I'm being shallow). It is certainly cheap enough. Since I'm talking about Cabela's stuff, I wiggled their 6'6" 4wt CGR rod yesterday, and it was magicial. At $99, it comes in at your price range, and I'm convinced these are gonna go down as cult classics.
The out of the box suggestion is a $20 Eagle Claw 3/4 6'6" rod. I have the 7' 5/6wt and love the carp out of it. You won't be throwing hero casts, but its cheap and a blast to use. It'll flex down to the cork, and fish on it are a ball, plus that soft action will protect the lighter tippets you will probably need to use.
Becker's RS4 is probably a decent all around rod, I'd certainly put line on and try it, but for my personal tastes, I can be pretty sure I wouldn't be interested. Again, YMMV.
...just go down to the swap threads and check it ou.t $115 and I will hand it to you personally
