I have a fairly decent rig too and always found it very noisy at home, it was only when I brought it into a quiet studio that the buzzing went away. Basically the problem is due to two things:
1) Electrical interference in the room (biggest problem) - caused by lights, computer screens, power adapters AND other appliances in the house (eg. washing machine etc). You will easily find out if this is a problem by moving your guitar around the room, you should find that it gets noisier and quieter at certain spots.
2) High gain settings pick up a lot of noise.... made even worse if there is electrical interference.
You may also have a ground loop going on. This can be very hard to find, the only way to do it is to unplug everything and add the units one at a time until the hum starts up.
One other thing you should do is make sure that you are using proper magnetically shielded cables. This is very important when running through a number of devices. Hope that helps.
