I was a bit confused about the mono compatible title and the topic. Mono compatible means there won't be any phasing issues when combined in mono, for example MS(mid-side) micing.
On the other hand I am working with an engineer now who is mixing
tracks meant for the phone, and when i heard them at first, they sounded extremely high midrangy. He explained thats how it will translate properly over the phone.
With that said, If the mix sounds the way its
supposed to sound, shitty speakers or whatever everyone else is using shouldn't have a say. There is going to be that one system that your mix will sound like crap on, so what, the owner wouldn't know anyways...
Ha.