I almost always break down cans by purpose and traits (i.e. open v. closed, IEM v. Full, Home v. Away) That makes a huge difference in which can is "the best" and which isnt. So Ill try to do generalizations.
Best Home/Full open under $80 = I pass on this one. To me the MS-1 at $100 is a far better deal than anything else at $80. Yes, its $20 more than the goal but having lived firmly in the under $80 camp and having lost far more than $20 in selling all the sub-$80 cans I had AFTER the MS-1, I believe its worth the extra. If you just cant swing it, the SR-60 is the next best choice. The SR-80 I disliked and wasnt worth keeping even though I got it new for $70.
Best Home/Closed = Again, nothing at sub $80 is worth it to me. The AT A500 is my choice here. Fantastic can for the money, esp. since its a rare GOOD CLOSED sub $100 can. I cannot recommend any other sub $100 closed can. Most of them were "meh" and some were downright terrible. I think one or two if the sub $100 Sony were supposed to be good but Im boycotting Sony after damn near everything Sony of mine has fallen appart long before its expected useable life.
Best Away/Closed = Without a doubt the AKG81DJ. I LOVE this phone. In fact, Im hard pressed to suggest anything else sub- $150, its that good. Portable (to me), SQ is excellent, decent isolation, its solid all the way around. I still dont think its worthy of being the best closed HOME can but its darn near close to it. Portable wise, no contest. It wins mightly.
Best Away/Open = IMO all it has to be is not so gigantic that its obtrusive (Im looking at you AT AD/A Series!) MS-1 still fits the bill here.
IEM = I think IEMs have the worst value to price ratio of any phones. I only suggest them if you MUST have isolation. If so, the iM716s are the choice here. Sound as good or better than the ER6s (to most) and some even say near ER4s levels. $70 too? Insane. If you need IEMs, grab em.
As far as the EP-630, was a decent deal. Decent SQ to price ratio but with the iM716 at $70 now, I cant justify not spending the difference. Would be great as a phone for every now and again but if you plan on regular use, go iM716.
There are about 100 other ways to classify phones so I wont go on any further. The best advice I can give is make sure your needs are your true needs and then hunt down phones that fit. If you can stand full sized open, youll get the best SQ most of the time. 2nd (IMO) would be a closed full, then closed portable, IEM. (if money is roughly equal)