Hey grinch.sid. Nice to see another trance/electronica fan on the message boards. I see you're from India, well I'm pretty closeby, I'm Sri Lankan,
though I'm in college in Canada right now. I had your same dilemma just a week ago. My B&O A8s broke down and I wanted a really good earphone with great bass. Well, after a lot of digging it came between the atrio m5 and the sleek sa6. The sleek sa6s are generally rated better than the m5s in terms of mid and higher end freqs in terms of clarity, range and precision. However, the atrios are supposed to have very good mids and good highs, but their most outstanding feature is supposed to be their deep, powerful, accurate, tight bass (that doesn't overwhelm the rest of the sound spectrum at all) which trumps all other earphones in its price range or higher price ranges. Also, I found that the sa6s (which are still a relatively new product) have some durability issues, and it is the general consensus that the atrios are more durable at the moment.
The listed price for both the atrios and the sa6s are $199 at soundearphones.com. However I emailed that website asking for a coupon discount and they offered me a $40 discount for the atrios and a $10 discount for the sa6s. Both earphones are said to have good isolation and comfort. The sa6s come with the added bonus of having replaceable cables for around $26 if you somehow damage them. There is also a wire less headset package that was just released for the sa6 which will set you back another $100 if you decide to purchase it Both earphones come with a 2 yr warrantee from the above website, and I hear customer service is very good, though you are living abroad, so you should find out how that works.
The fundamental difference between the two is that the atrio uses a dynamic driver which supposedly gives a warmer, more natural sound while the sa6 uses an armature driver which is more precise and analytical.
It was a very tough choice between the 2, but since durability and great bass were my top priorities, I got the atrio m5. It is being shipped to me as I write this. I can't wait to rediscover all my electronica on awesome sounding phones! I hope this post helps.