Hey, nice post...I don't know much about the B&W P7 other than I tried them at Best Buy I believe and just didn't like the fit or comfort. Too stiff and the clamping force was a bit tight. But it's just a personal observation. I didn't get a chance to test the sound as it wouldn't have mattered to me given the discomfort.
Re the Meze 99...I can tell you that I have very neutral sounding headphones (Stax, Sony MDR-CD900St) and the Meze is a great alternative to that sound without sacrificing detail. It has an excellent bass impact (the "fun" aspect as you say), but it's not muddy or veiled sounding at all. The mid-range is one of their strengths. I've also been using them with my iPhone and Dragonfly Black and it is pretty powerful sound. The Meze is a sensitive headphone thought that doesn't need that much juice. In fact, I rarely have to go above three bars on volume when using the Dragonfly Black. The only caveat to the Meze is the ear pads might be on the smaller side - it wasn't a bad fit, as the pads are soft and plush, but I opted to purchase the larger pads separately from Meze and it works out a bit better for me.
Re the Meze 99...I can tell you that I have very neutral sounding headphones (Stax, Sony MDR-CD900St) and the Meze is a great alternative to that sound without sacrificing detail. It has an excellent bass impact (the "fun" aspect as you say), but it's not muddy or veiled sounding at all. The mid-range is one of their strengths. I've also been using them with my iPhone and Dragonfly Black and it is pretty powerful sound. The Meze is a sensitive headphone thought that doesn't need that much juice. In fact, I rarely have to go above three bars on volume when using the Dragonfly Black. The only caveat to the Meze is the ear pads might be on the smaller side - it wasn't a bad fit, as the pads are soft and plush, but I opted to purchase the larger pads separately from Meze and it works out a bit better for me.