Hey T1, I recommend you get the Beyerdynamics T1 for sheer coincidence.
Oh wait, those are over a grand. o_O
Seriously... if you wanna start off with headphones you'll never wanna replace:
1. Astro Mixamp or AX720 ($130)- Gets you started with virtual surround.
2. AKG K701 or K702 ($250) - These are a competition joy, and bring a ridiculous amount of clarity and soundstage. If you're looking for something mainly to kick ass in FPS games, this is it, but only if the AD700s are out of the question.
3. DT990/600 ($229)- These will be good for both music AND gaming, so if you're not ONLY playing FPS games, these would be the ones I'd suggest, as you'll undoubtedly use them from everything between, music, movies, and games.
As for the E9 ($130 alone, $200 with the E7 through Micca Store), this is an amp you'll most likely want if you don't have an amp to power these hard to drive phones for music OR if you plan on adding a mic to the headphones when using them with the Mixamp.
Remember, the E7 is essential to use with the E9 if you listen to music off your PC and don't have a good soundcard. If you do happen to have a good soundcard, you can hook up the E9 to the soundcard's line out, and skip the E7.
You may wanna check the first post in this thread, if you want something just purely effective. My recommendations in this post is based off the countless headphones I have gone through, and only to those willing to spend at least $500 in one shot if they have NOTHING atm.
I'd personally start with:
AX720 ($130, brings a headset for voice chat. Even if you don't like it, the AX720 amp compares to the Mixamp for the same price.)
K701/2 - or DT990 if you don't mind sacrificing a little clarity for bass and immersion.
E7/E9 - amp/dac for music, and powers my phones for gaming.