Strat, welcome. As the graphs which Rich Goldstein linked illustrate, it could reasonably be argued that the M3s have slightly better bass response than the Era D4s, aside from the effect of the even more pronounced upper-bass boost which the Era has around 100-200Hz. This gives an impression of better bass, both for bass fundamentals in that range and the upper harmonics of weak lower bass notes being louder lending an impression of lower extension than actually exists(a well-known effect which makers of small speakers often employ).
As was already suggested, a little more room reinforcement can be had by placement 3-4" from the wall behind, which is still enough "breathing room" for the ports. Generally, with room reinforcement speakers such as the M3 and M22 will have good response down to at least the 50Hz area and users(including me)find that reasonably adequate for most music(pipe organs excluded)even without a sub. Of course, as was said, a sub helps even on music.
