Looking at decent audio for my PC

Amp is important cause you can use headphones of different impedance but mostly for music listening but it is really great for music

You could go for something like a Xonar D2X with a pair of Sennheiser HD595 Headphones. I am currently selling a Xonar D2X for $160 shipped (shameless self plug). I know you can find a pair HD595's for about $150 as well (take a look at Ebay). This would land you roughly in your price range while offering great sound. I personally used this setup for years and loved it (I am currently in the process of upgrading). The HD595's don't really require an amp to run well, although mine have benefited from the addition of my FiiO E9. You could easily run the setup I described and than add in a dedicated amp later if you feel like you really need it.

I have also used those Zalman clip-on mics and they work just fine. They aren't anything amazing, but they get the job done and the sound decent enough especially considering the cost like $5.

I can vouch for the excellent sound quality of the Xonar D2 series cards. I have the D2/PM which is the PCI version of the card. The D2X is the PCI Express version of the same card. The D2/PM resides in my girlfriends computer along with a set of modded BX5 speakers that I did for her. I use the Xonar Essense STX card which is slightly modded Along with a modded Tannoy TS10 sub & modded M-Audio BX 5's. No matter which system we use the sound quality is excellent.

The D2 series card does not have a lot of power for driving headphones. You will get adaquate output with high sensitivity low impedance phones but not anything else. Thier ouput is D.C.coupled which is good & they have low D.C. offset so you can drive any amp with this card even D.C. coupled amps that have reasonably high gain.

Whether your headphone can be driven is affected by two things: impedance and sensitivity. High impedance needs more voltage to drive, and low impedance but hard to drive cans need more current. And there are amps designed to focus on driving either type of headphones. But there are phones like AD700, SR60, or ATH-M50 that has low impedance and high sensitivity, allowing them to be driven off of a simple portable players or even headphone out of your computer. If you are just starting, and want to stay away from stepping far too into unknown, costly territory, especially in a field of audiophillia where hype of a product is so very common, I advise you to start by getting a cheap, well reviewed headphones that can be driven straight from your computer or portable player.

If you're planning to use your headphones for gaming, I've read several reviews that said it has pinpoint positioning ability and is very good for game, but like you said, lacks bass. Perhaps telling us what type of music you listen to, or what you seek most in headphones (whether it be bass, soundstage, detail, etc), would let people to help you more effectively.   

Hi, I would suggest you look at an external dac such as an emu 0404 or 0202 or possibly a zero dac.

Also it would help if you could list some musical preferences, because for rock I think grado sr225i's would be absolutely perfect and they do not need to be amped.

For bass heavier genres ultrasone's would be great.