Jarkko Mattheiszen
The FU guy.
Before you venture further into the land of parallel compression (though it is an extremely powerful tool), you should keep in mind that an aggressive, good hi-gain metal guitar tone comes both from the guitar and the bass. They have to complement each other, not stepping into each other's territory but still supporting one another. It's not that easy to achieve, and IMHO a good bass tone is something often overlooked in these kind of situations.