MSR7 is not neutral and it is indeed bright,
I haven't heard the T50RP MK3, but based on the measurements at Innerfidelity,
As for a headphone "slaying" MSR7 in sound quality, I personally have yet to hear one.
First let me say that if people here are going to rate headphones against other headphones, and they've never owned them or heard them, and are using "measurements" as their criteria and proof, then i have a word for that kind of nonsense, but, i'll not use it in such polite company.
So, let me be clear........Unless you've owned the phones, you dont know what they sound like, and this goes for people who tried them briefly in a shop or at a show.
You literally have to buy them, own them, and use them for a while to know how they sound., and this is why i'll never post a review or a comment about a gear which i've never owned and try to judge its value and sound based on online measurements.
Frankly, thats ridiculous.
Here is the thing about "measurements"....
They are just numbers and numbers are fine if you are a computer, but when you are using ears in real world testing situations to determine what sounds best, then just get rid of the numbers as they are basically useless "in real life" criteria.
For example, this idea you have that that R70x has bass rolloff, because of numbers...
Well, thats fine for a computer to say, but if you hear the phones you'll discover that the bass reaches deeper, is larger, and is more profound in resolution then the bass offered by the MSR7s.
Thats a fact that your ears will prove which will dispute "numbers" or "measurements" every single time.
And that you've not heard the R70x is the literal reason you can say that you've not heard a headphone that can slay the MSR7 in sound quality.
But i have heard it, as ive owned them both, and tested them both, and so i can tell you that the MSR7 is a great headphone, that is bright, analytical, and does not have a natural sound in the upper mids, or overall.......It has a very good sound, but it does not reproduce music without adding its particular tweeked upper mids to the sound, and it has a slight bump in the bass.
So, when we talk about good sounding headphones, then often we are describing how a certain headphone recreates the music according to ITS particular EQ'ing and that is what you have with the MSR7..........However, when we are speaking about 'audiophile" sound, then we are discussing a different concept, as "audiophile" does not mean "great sounding", but rather it means perfectly accurate related to transmitting the source accurately.............In other words, it means...."this is how the music sounds"....vs, "this is how the headphone recreates it to sound according to how the headphone has been EQ'd to reproduce sound".
So, with the MSR7, you get the bright and very very present EQ'd sound which sounds great, but with the R70x you nearly get the straight wire and THAT is why its a better headphone and a truer headphone and a audiophile- reference headphone as compared to the MSR7 or as compared to nearly any other headphone that you can buy.
And regarding the Fostex T50RP-Mrk3.......well, you've not heard them,you've not owned them so, its best that you dont review them or compare them, until you do.
I hope this makes sense to you.
However, Ive owned them and ive literally compared them to the MSR7 and im telling you and any reader that they are a ridiculous value @ $150USD and that they sound as good as the MSR7, but have a slightly wider sound with more air because they are not a closed headphone.. which results in a perceived very slight loss in resolution...BUT, if you listen to their sound, then you will notice how much they do sound like the MSR7.
The attractive MSR7 is better built, better accomplished, yet, the Fostex T50RP-Mk3 sounds very similar yet more open.....does it sound better?...No,.. but, for the money and if you are making the decision between the 2, then get the Fostex......However if you want the best for the money, then order the AT R70x as its much better then both of those.