Been a big Westone fan since I moved from Shure E530PTH to UM2 when it first came out, then UM3x, UM3xRC, W3, W4, W4r, UM Pro 30 and W60, so I really wanted to like the Pro 50 but couldn't.
I have been comparing the ATH-E70 (with comply tips supplied) against my K10U (using the AK240 unbalanced out), they do sound very similar, especially in the bass department, very deep low frequencies extension, probably better than the SE840 (as I remember my K10U beat my SE840 in bass extension) with just as much details in the highs. The only difference is that the K10U has a little more low mids, which makes the overall sound a little thicker, which could be a good or bad thing depending on one's preference.
Comparing with the Pro 30, my everyday go to IEMs, the E70 definitely has a lot more high frequencies details (I think the Pro 30's trebles start to fall around 6-8kHz), the low mids and bass are similar to my K10U but with less low extensions.
So considering I paid less for the E70 than my Pro 30, they are super good value for money in terms of sound quality. However, not sure yet how well built they are comparing to the Pro 30, I'd still prefer to use my Pro 30 on the go, they are just so comfortable, compact and convenient to use in my opinion.
Out of all the IEMs I own ( you can check them out in my profile list), I'd consider my K10U (older non-metal version) the most balanced sounding, probably the E70 a close second, I'd use them to mix and master music if I have to. W60 is a completely different beast, they may not be very balanced or neutral sounding, but they make music very soothing and enjoyable to listen to.