So I would say 4 or 5 wt would most likely fit the bill. I might lean toward the 5 if you are catching a lot in the 18-20" class. I really like the Dan Craft Sig V line, and the FT blanks are supposed to be awesome as well. Since I've started wrapping my own, I haven't really kept up with the factory built stuff, but I've heard a lot about the Cabelas 5 piece stowaway line and Temple Fork is a hot line too. But I can't say I've used either personally. I guess a lot would depend on how fast you like the action as well.
I hate to comment on reel selection, because I'm one of those who sees the reel as a line storage unit in most applications, so I cringe at spending $150 or more on it. The good news is that there have been a lot of new reels on the market lately that are very decent reels without spending outrageous amounts of money for. Cabelas, Bass Pro, Redington, Echo, Okuma, Orvis, STH, and Scientific Anglers (I'm sure I've missed others) have all entered into this range with decent models. Are they the same level of quality machinery as a $350 reel. Most likely not, but do you need it in real terms on the river? Probably not, but that's something everyone needs to decide for himself and his wallet.