I have both the a900x and a500x.I bought the a900x the day after buying the a500x because I was so impressed by the a500x.
They are both quite nice but the a900x has more detail, is far superior generally , and is well worth the price difference IMO.
I personally find the a500x the most impressive headphone I`ve tried in it`s price point though.
Incidentally, when auditioning the a900x I tried the a1000x as well. The difference between those was not nearly as clear as the difference between the 500x and 900x.
Not at all worth the upgrade price (also IMO).
If you're really interested in the a500x I intend to post mine in the for sale section tomorrow.
LOL, I'm just thinking that shipping would cost nearly half the cost of A500X or even more
When I bought M40x from flipkart.com for INR.7199 (USD.116) the A500X were available then for INR.6959 (USD.112) and a week later the same A500X's were available on Flipkart for INR.5000 (USD.80) --- I went crazy