I just got the Sennheiser 595's and I want to say they sound awesome. I wanted a decent pair of headphones that I can use late at night to keep the house quiet while I'm on my Xbox 360. After some thought - and much reading I opted to go with the higher quality stereo headphones over a potentially weak sounding 5.1 headset. Admittedly I'm not an audiophile (I'll buy something without even listening to it based on other's reviews) but these do sound really great. I listen to a fair amount of music so I didn't want to sacrifice music for gaming.
I listened to several cd's this weekend and heard detail I've never heard through my HSU ventriloquists. I have an Onkyo TX-SR601 receiver driving them currently. So I do recommend them as well and I appreciate all of the posts helping me with my decision. It seems like anytime these days when you make a statement there is someone waiting to flame you. But I am glad we have a forum like this for the open exchange of opinion.
I also just got the Zalman Microphone and did the mod to the controller so I can use it instead of the cheap Live headset. The only thing I've done so far is to make a couple of audio messages to test it - mainly to check my soldering skills.

It seems to work fine but I had to hold the mic right up to my mouth for a decent volume. That said, the audio was very clear. As yet I haven't really had any online time to check out how the mic sounds to others. So I am curious too if anyone has had any experience with the Zalman - especially using it online.
Also I'm considering getting the JVC surround sound adapter but I really don't want to sacrifice audio quality for surround sound. I guess that's something you have to hear for yourself though. Can those with the JVC adapter chime in to say if they are happy with their decision to buy it?
Thanks