I'm getting a new rig and have decided I need better sound. After research I've come to the conclusion I will get the Sound Blaster Z and a decent pair of headphones I'm thinking...

First check to make sure all your drivers are up to date.   If thats good to go than I would check out this http://www.thesycon.de/deu/latency_check.shtml   I'm not an expert by any means, but I've had crackling before and it was a cpu issue.