Need A Recommendation ~$160 Sennheiser Not A Option

Beyerdynamic DT770's in 80 Ohm fit your requirements perfectly. The most viable options would probably be those and the M50's you mentioned.

You can get the DT770's from cobrasonics on ebay for under your price. They have a good reputation here and are reliable. But they only list 2 at a time so they sell out fast. Just keep your eyes out and they'll have them listed. These headphones benefit from amping more than the M50's do, but they sound decent without an amp compared to other headphones at a similar price. Do a little sleuthing of comparisons between the two, they're very close. For my purposes I chose the DT770's, but you might find the M50's fit you better.

For DT 770/880/990, and Sennheiser HD 600's, a lot more deals are on Ebay than they are on Amazon. I've seen the DT 770 being sold for 130-150 fairly regularly.

Haven't heard the MDR-V150's, but I can tell you that the DT770s are very comfortable and block out noise well. From what I've heard, the M50's block more noise, but they are much less comfortable.

 

Just saw that you added that you're looking for headphones that aren't bass heavy. The M50's and DT770 80 ohms do have boosted bass, but it isn't an insane amount. The 250 or 600 ohm versions of the DT770 are more neutral, but they have a greater need for an amp. If you're looking for neutral closed headphones, you could also look at the Shure 840's or AKG K550's. The Shures are not as comfortable or durable, though, and the AKG's can have seal problems and will be difficult to find within your price range (used, maybe?).

Bose AE2 would be my initial suggestion - excellent passive isolation (better than most closed headphones), comfortable, and they sound good enough. They aren't perfect, but they should satisfy what you want (I'm noting isolation as a primary desire). Less money, I'd look at the Koss DJ100 or MV1 (MV1 will isolate more, and sound better, but need an amplifier unless your current device can handle their 250R nominal impedance (they're inexpensive enough to give you a few bucks to grab a FiiO amp though, so I wouldn't write them off)).

M50 would be fine too, they're less comfortable than the AE2 imho (they're heavier and clamp more), and have a lesser soundstage than many headphones ime, but provide decent passive isolation. They also probably cost less than the above options (except the DJ100) - as far as which one to buy, the version differences relate to color (black, white, or the silver/blue limited edition) and cable (straight or coiled); it's basically down to preference as far as which one you want. IMHO the limited edition are the best looking, but if they cost more it might not make sense just for aesthetics.

You could stick with sony and get mdr-7506's, there amazing and block noise fairly well plus the don't require an amp.

They'll run you $70 shipped to the US.

http://www.jaycar.us/productView.asp?ID=AA2065&keywords=pro+monitor&form=KEYWORD

 

You cant do much wrong with the M-50's either(specially when they can be had for ~$100); but I'm finding more people recommending the Monoprice DJ cans instead.

Op, look into the Ultrasone Pro 550. 

The obvious step up for you would be the MDR-V6. They sound better than your V150s and have improved design and sound isolation / leakage. 

How about the V-MODA m80, or if you prefer bass heavy music, the lp and lp2