- Sennheiser PC360
- Beyerdynamic MX300
- Sennheiser HD555/595 + Siberia mic (forget the zalman, it's horrible, the siberia clip-on beats it handily)
- AudioTechnica ATH-AD700 + Siberia mic
On a budget, I'd even consider a Sennheiser PC161 headset or a Sony MDR-V6 with Siberia Mic.
If you go with seperate headphones and mic, then also consider the Sennheiser HZR62 inline volume control. It's a life saver if you are used to having volume control on your headset. And the Sennheiser HZR62 even let's you adjust the volume seperately for each channel. A true godsend!
So, in essence, under $150, you could get the ATH-AD700 headphones ($90), the Siberia Microphone ($15) and the Sennheiser Volume Control ($25) for a total of $130 plus shipping. This setup would be on par with the Sennheiser PC360 or the Beyerdynamic MX300 as far as gaming goes. It sure would beat any other "gaming headset" out there handily (except maybe those two mentioned).
another vote for the Sennheiser HD555's. I picked up a pair when they dropped under $100 and they've lasted well with a lot of abuse. Sound stage is perfect for shooters, which really helped. The cord is also replaceable should it be damaged without too much hassle. I had the 160's or the 155's (not sure) before and snapped the band, best thing to ever happen