Well, there are many choices, and it all depends on what you are looking for.
The kits from Dynastar, Estes and Madcow Rocketry are some of my favorites.
However, you find some kits from Binder Design ( Excel Jr, Spike, Aspire), PML (Io, Calisto, Exployer) and LOC ( Aura, Weasel, Legacy) great for mid power, and technically could take you into High Power down the road. For example, I fly my Io on F-H motors, and feel very good with that. However, my Rising Star by Dynastar has like 70+ flights on it, using everything from a C11- to a F motor. I am currently replacing my Rising Star with a new one, and building a Madcow Striker, which I really like as a "mid" power flyer. I personally like large diameter, heavy rockets so I don't have to chase them very far. However, I have a few minimum diameter rockets that, well, shall we say, go out of sight.....
It is all about personal taste as far as which rocket you like, that's the beauty of this hobby, you can build and fly what you want, that meets YOUR guide lines.
Enjoy
