Thamuza,
Just a wanted to share my way of looking at slowly upgrading my tools.
I have 90% cman sockets, and they have served me well, some I have had and used hard for 10-15 years, so I have left them alone.
I have been upgrading my most used tools, specifically my ratchets to snap-on. I have no regrets, in fact I have even bought some SK ratchets for backups just because the cman ratchets now seem so clunky when compared to the snap-on ratchets. the SKs are a good solid ratchet, and while they may not be as nice as Snap-on ratchets they are reliable.
Wrenches on the other hand once you get some quality ones you will never look back, I prefer the feel and quality of SK superkrome, I have nearly replaced all my Cman RPs with them and couldn't be happier.
I also have been upgraded other failure prone items like bit sockets to Proto and Sk and love them, probably not as nice as Snap-on, but the price is good, and they perform very well.
Bottom Line IMHO, slowly upgrade or expand your collection where it counts, based on what you use the most.
And just to answer you original question, I consider these to be the beast examples of "mid level" tools, mostly on price, quality if often close to snap on. SK, Proto, & Williams. (I left out a few brands b/c I have never used them, and can't offer an opinion on them) Wright, Armstrong, Bluepoint
-Sam