Get a Mic and headphones. You could save money and you get a better sounding system.
Muting can be done in several ways and a mute button comes on nearly every microphone I have purchased. HotKeys, Software and by using push to talk. It really isn't a issue, not to mention that headsets that come with a mute button are on the hefty side of the price tag.
There's no volume control on the headphones,.
That's a point I didn't think of. My £24.99 headset has separate volume controls for the level of voice chat and the rest of the game sound. This is very handy. It's a facility I would lose with headphones and separate mic.
That's even more impressive than I meant, mine literally doesn't even have an overall volume control! .