Alright, well, to save you a few years of frustration: you will never re-create live-sound acoustics (especially with headphones).
Now that we've taken that off of the table, let's address what we can fix: leakage.
The biggest problem you'll run into in switching to a closed-back headphone is a smaller/worse headstage - you also tend to pay more for the sound quality (at least in my opinion). At around $300 there's not a lot that comes to mind that won't leak; the Denon may address the problem but they are an entirely different sound signature (they're very much a "v-curve" headphone with sucked out mids - not to the insane levels of some other v-curve headphones, but that's what they are). There's a Kenwood that costs a bit more (KH-K1000), isolates a bit better, has very good mids, but (I'm assuming you live outside of Japan) it's a special import item, so you're basically stuck with them for better or for worse (you can resell them at a loss, of course). I like the Kenwood over the Denon, but it isn't my top-pick as a headphone.
Beyerdynamic makes a few closed-back models, I've only heard one of them (the T70) - it wasn't bad but I don't consider it to justify the $500-$600 price-tag when contrasted to the Kenwood (the Kenwood are smoother and have more low-end presence, the T70 are somewhat more accurate).
Going into the land of things-I've-never-heard-but-would-consider-if-I-was-in-your-shoes:
- The Beyerdynamic DT770 (which costs less than the T70, and looks to use the same housings (it has different drivers and I'm assured it sounds quite different)) should isolate fairly well (again, based on the T70). It will probably be a night-and-day difference from the HD 555 though.
- The Audio-Technica ATH-A900 are supposed to be good for jazz and don't cost a whole bunch, but will probably not fit you if you have a tiny head.
- The Sony MDR-CD900ST are supposed to be something exceptional in terms of tonal balance and detail retrieval. Some reviews have compared them to the AKG K701 or Denon AH-D7000. They are, like the Kenwood, a JDM product. The upside is, they cost a lot less. They're designed to be studio monitors.
If it was me, I'd probably try the A900s first - they're probably the cheapest option I've mentioned and you can buy them from places like Amazon.com and HeadRoom (which let you return items if you're unhappy); if you hate them for whatever reason, then look at something else. If you decide on the Beyerdynamic models, and don't intend to purchase an amplifier, look for the 32ohm variants (for the T70, that's the T70p; for the DT770 you just want the one that says 32 ohm). The Audio-Technica and Kenwood (And there is speculation that the Kenwood are actually a re-branded Audio-Technica, but I've never heard a general consensous on which model; the ATH-A950LTD, A900LTD, and A900 Ti are usually the top picks) are both 40 ohm models, the Sony is something like 60 ohms but should still drive from anything (don't take this to mean impedance determines all - look at efficiency as well (and you'll find that everything here is silly efficient). If you're going to buy an amplifier, the Fiio E9 is a good choice if you have wall power available and intend the thing to be set-up at a desk. If your computer/whatever sucks at producing sounds, there are USB external solutions, and PCI/PCIe internal solutions, that would be equally suitable. An example would be the Asus Xonar DG (internal) and the Fiio E7 (external).
Quote:
Originally Posted by
compoopers 
Thank you for the reply. I will try to get studying.
Mainly what I am looking for is something that can accurately represent what the band sounds like as if it was like it was happening again. I want accuracy but I also of course want it to sound good (before I get in over myself with tedium). To give reference I have been using the HD 555s and have had no problems or qualms with the sound. I recall reading that HD555s are well balanced, warm headphones, but I'm not sure.
The reason I am looking to upgrade in the first place is because I need less leakage. I love my 555s and honestly I'd just keep using them but if it were me on the receiving end, I would get pissed at a roommate who used them late at night because they leak so god damn much, even at the lowest volumes you can hear them.
My price range is preferably 300 or less but I can stretch if it's really worth it. I don't have any amp or DAC but I could invest in them if what's needed isn't too expensive.
I just want good jazz sound.
Edited by obobskivich - 2/9/12 at 7:58pm