I won't buy Sennheiser again because they are jerks. Also, the $200 pair of Sennheiser headies I bought aren't as good as my $50 playtronic ones, IMO.
I got myself some 448's and while the build quality seems balls for the price, the frequency response difference is quite noticeable compared to my cheaper headphones I was previously using. I can actually hear people sneaking up on me in MW2 even if they have ninja pro on because you can hear the grass rustling.
They're pretty light and comfy and don't require me to buy some stupid external amp, they run just fine plugged directly into my sound card on the computer, 1/4 - 1/2 volume in windows' mixer is all I need.