Whenever I record CSS with fraps, sound is very low and I cannot put it any higher, I can only switch fraps to record from stereo mix and line in, and it works on both, except the sound is low, when I put it on stereo mix, and put the choice in the volume control (recording) to stereomix and then come back from the game after recording, it automaticly switches to line in.

It switches from Stereo Mix when joining a server for me. Try starting the demo then start recording after the map has loaded (You can pause the demo and start from the beginning, etc).