Your best bet would be between E30 and M1 as the others are out of your budget and M1 to M2 is a minor upgrade. So no point in shelling out 1000bucks($20) more as you said you are tight on budget.
E30 & M1 are excellent sound quality wise for the price and you cant go wrong with either of them. In fact i would say they are the best in their price range.
the only difference i could make out between the two from my listening was in the treble part. e30s really shine here with nice sparkle in high frequency range. m1 is equally good but with a bit of less sparkle.
in mids department the difference was not much noticeable to my ears. i guess vocals are more clear on e30s.
e30 has neutral sound whereas m1 is a bit on the bass side without compromising on the mids & highs. you can say a bit softer in tone reproduction relative to e30 or more fun sounding.
e30 over m1-
>slightly better in detail
>sounds more airy & open with great imaging and instrument separation is slightly better too.
>extremely comfortable once you get a good seal to your ears(would rather say comfort king like the old PL30s).
>strain reliefs are colour coded(red for right,blue for left) so one doesnt need to search everytime which ones right/left. just put them on seeing the colour.
m1 over e30-
>bass is more in quantity.
> better build quality--m1 has rugged cable where e30 has rubberish.
> u get a hard case to put them safely instead of the leather pouch with e30.
> isolation is somewhat better (e30 has mediocre isolation)
so if you want more detailed sound with excellent comfort and can compromise a bit on build quality and isolation--go for e30.
if you want better build(cables),a hard case to put them safely with better isolation and slightly less detail--go for m1.
its a matter of preference.
But recently my brother had to get it replaced twice as the 3.5mm jack on M1 easily gets damaged and some issues have been reported in the recent past by people.
personally i go with e30 as i cant compromise on sound have been using them for around 8 months. i like to explore detail in music. i am fine with its build. only gripe is soundmagic should have included a hard case for it.