Denon AH-D2000 is a brilliant phone and I got mine for around $230 as well. They are hard to match. However, they aren't very portable as they are a semi-sealed headphone. Which means the back is covered to block out some sound but it bleeds pretty well in both directions. I recommend them as a home set.
However, I have other suggestions.
Sennheiser HD-25 MKII is a legend in the headphone community. It's loved and used by people all across the board and is a very popular DJ headphone. It has great sound and superb build quality. Also isolates pretty well. You can get these for around $200.
The suggestion of the Beyerdyamic was a good one, too, as it's considered a slight successor to the HD-25 as it has an all-around better sound. They will cost you more, though.
If we move away from over/on-ear headphones we get into IEMs. These have the benefit of providing strong sound with the best isolation. However, some people don't find them as comfortable. I'm not one of those people but some are.
In that area I'd recommend Shure. For that price range they offer some solid options. If you want to stay less expensive I'd also say looking at what you can get from Ultimate Ears. The Triple.Fi can sometimes be found for that price range and if you can manage it they're one of the best sounding IEMs you can buy without going custom.
The thing is, every single one of these headphones will give you better sound than any Beats headphone. Beats aren't known for their quality here on Head-Fi because people here tend to want more than over-powering bass with weak everything else. To most headfiers, Beats sound muddy and that's kind of on purpose. They're a fashion accessory, not a serious headphone.
At the end of the day, here's the short of it: When you ask people why they bought Beats they'll say, "Because so-and-so wears them and he's famous so he must know." When you ask someone why they bought a set of Denon AH-D2000's they'll say, "Because they sound like they should cost twice what they do."
