If you want bass, I really like the Beats Studios or Pros. I would try them out at best buy first and try them, then go to this site to get them at discounted prices:
http://www.monstercable.com/outletstore/linelist.asp
That's to Monster's outlet store, you can get beats for half the price ($150 for studios, $200 for Pros) and they are refurbished. They are 100% real as well. Trust me, I own both the pros and studios and they look brand new and come with everything except the original box.
I know a lot of people are against them but most of the time its that they are not because they are terrible headphones but not so good compared to what they are priced at, $300 studios and $400 for pros. But for half price they are comparable to really good headphones.
A lot of people will suggest headphones to you which are great but often will need an amp of some sort to give you that bass that you want. Example is a fios amp.
The question is, what will you use them for? Computer use? Studio? Or do you just want to listen to music on your iphone/android? Are they mostly going to be used at home or are you going to be used more outside?
If you are just someone who wants good headphones but will use an iphone/mp3 player I would go with studios because they have a battery that will power an amp and are more comfortable than the pros. The battery on most phones don't have the juice to power headphones to make them sound good so this is a plus especially if you are wanting that bass that thumps like a system in a car. Sound does leak, so if you care, people can hear what you listening to.
They are made of plastic so there are complaints of quality but mine have been great for the past year and the only thing that needs to be replaced were the detachable wires (you get two with studios, a regular red and a black sonic talk for cell phones.) Though this is inconvient ($20 refurbished wire) its good that I can just replace the wire and not the whole set if the connector goes bad.
If you want the best sound, the pros are the best sound overall. Hits hard bass and has good highs and mids. They sound fine on my phone and do not require batteries. They are not as comfortable as the stuidos and are bit more bulky so they are not as portable friendly as studios. Quality wise, they are built with mostly aluminum and leather and I have no doubt that these can last me years. Sound leak is very small and you can barley hear to what I'm listening to.
I've connected this to my amp on my computer and they sound amazing. My favorite cans for music that has heavy bass in it. Music just sounds amazing. It does get uncomfortable about a couple hours of use and will have to take them off since these sit on your ear rather than around it like the studios do. They are also heavier than studios.
I know there are really good headphones out. I have tried a lot, dennons, sennheisers which are great but lack the bass hit that I like in hip hop music. The beats fit the mode for me. Also keep in mind that a lot of these headphones are built for studio and a lot of the times will have a 3.5 jack connector. So if you were going to use them for ipods/iphones then you'll need an adapter which gets clunky and don't sound great unless you have an amp to power the cans in most cases.
But my advice is that every ear is different and the only way to find out what you like is to test them at a best buy to the music you listen to. If you are like me who enjoys hip hop/electronic, I do suggest the beats but not at brand new prices. Definitely check that website above. Rock or music that concentrates on natural sounds like voice and instruments then I suggest denon's and sennheisers. They have a more wholesome sound and acoustic guitar especially sounds very nice.
I personally own Sennheiser 595 hds and use them a lot but I connect them to my computer through an FIOS 7 amp. I use them for listening to movies/tv and if i'm listening to music that focuses more on the highs/mids like acoustic guitar for example.
I'm not an expert in this field but hope my experience with them helps with your decision. One other note, DO NOT waste your money on Solo beats. They are all bass and sound like crap compared to Studios which will be $50 more on the site are far superior.