I have had a pair of Monitor 7Bs for my 2.0 system since 1982. At the time, they were about the best bang for the buck ($400/pair). I just got a pair of Monitor 40s for my HT. Just for kicks I hooked one up to my stereo (Yamaha receiver) in place of a 7B, pushed the mono button and used the balance control (remember those?) to pan back and forth.
Here's what I heard: the 7B had way better bass. The 40 wasn't bad but with the 7B I could feel the bass drum as much as hear it. The 40 had a slightly better top end although it might have been due to the lower bass output. Overall, they didn't sound all that different to my 61 year old ears. :D I'm sure I'll be very happy with the 40s in my HT, especially at the Newegg price.