ProtegeManiac
Headphoneus Supremus
I'm puzzled by "distorted bass." The bass on those - and Prestige series Grados in general - might be weak, but I never drove any of them to the point that distortion was immediately audible. Maybe that one time my portable amp ran out of juice and I plugged it straight into an iPod Video but even then it wasn't that bad. Slow, maybe, considering that the Little Dot MkII at home could have reasonably articulate double pedals and bass lines at the same time, but never "owww switch it off now!" distorted.
Unless...the weak bass is getting compensation by boosting too much bass EQ at the source (a computer)? If yes, try switching off the EQ and other sound processing software first; if no, and the MS1 sounds fine, look into the possibility that there might be something wrong with the drivers (like grattle, etc). Then again, if you have to ship them back anyway, getting a replacement unit might not be economical if you already have the MS1. I can't think up how to explain "lifeless" aside from amp mismatch as @chrislangley suggested, but from my time owning the SR225, it was anything but lifeless, even with just a portable source; you might lose bass and percussion but the "bite" to the guitars (vs other cans) was always audible.