The test results are in and I'm happy to report that my cable modem speed has jumped to 3867/349!
And it only costs $10/month extra.
My friend Joshua just told me about the upgrade. You can get from Comcast by calling them and saying that you want the higher speed 4 Meg internet upgrade.
Do the speed test over at Broadband Reports before and after the upgrade to see the difference. You've got to be a member to perform the NJ test. That one gave me the best results.