On the lower end of the cost spectrum you might check out a used pair of Monitor Audio Bronze 2 speakers, Generation 5. They just barely fit your depth requirement, have a 6.5 inch woofer and are front ported so you can place against a wall, although in my room they sound better 6 inches off the back wall. I have them placed on 8" stands on my desk. The Bronze 2 specs claim a frequency response of 42Hz - 30KHz.
I find these easy to listen to for hours at reasonable volume.
These replaced a set of KEF 100's that were way too bright in a nearfield situation.