Stereo & Electronics - replacing front speakers

I am replaced the front 2 speakers in my 2000 z28 with Pioneer 6 1/2. For some reason they sound like shit specially with the bass. Does anyone have a clue why this is? If I wired the speakers wrong could this be the reason?

Because the Monsoon head unit is at 2ohms while your speakers want 4ohms.

http://www.fbodyaudio.com/articleviewer.php?article=4thgenfaq.tech