Not that I'm aware of. The Atrio MG7 has more sub-bass and less mid-bass it may end up not having enough mid-bass for you. It is also less strong in the midrange and less musical than the Yamaha. EQing might indeed be the best bet.
The problem is that you need a benchmark (or, preferably, several) to know what is too lean, too bright, or too edgy for you. I thought the Yamaha EPH-100 was pretty safe on the treble front but if you read back a few pages there have been some who even found that to be too trebly. A safe choice if you're worried about these things would be something like a Westone UM3X or even W4 but that's a different price range entirely.
I have a question, I got the 8320s at your suggestion, and I really love them. But, I really wish they were smoother on the back, those jagged edges hurt like hell! Is there anything in the ~$20 range (a little bit more is okay) that sounds just as sweet but has a smoother back side with fewer jagged edges? I've got about 15 hrs of transit coming up and could use something to block out the world.
Have to wonder how thick the housings are - perhaps a file and some sandpaper is all you really need...
I don't think anything I've heard performs quite as well as the Monoprice with a similar signature in that price range - that's what makes the Monoprice special (aside from the terrible ergonomics). If you're willing to give up a little clarity, perhaps you can try finding a MEElec CW31 for <$25. It's got a nice and 'safe' signature - very smooth, a touch of bass enhancement - but more importantly is very small and comfortable.
I just thought I'd post it. I emailed monoprice and asked that if they work closely with their manufacturers, and it was possible, that they perhaps redesign the 8320 very slightly. First, a smooth back to the case. It can be the same shape internally, but remove the sharp edges, and replace the microphonic cable with something slightly nicer. They said they would compile user feedback and consider a redesign!
The 8320 is likely an off-the-shelf OEM design from a company called OVC in China (they used to sell a few IEM/headphone models under their own brand). I highly doubt a redesign will happen considering it's sold for just $7 but we can hope...