[font=trebuchet ms]I use the DiMarzio DP101 Dual Sound in one of my guitars. It's a 4-wire version of the DP100 Super Distortion. I recommend it because it gives you more options in addtion to the series-connected humbucker tone of the SD. These are passive pickups. There's no preamp, and no need for one.

The only problem I can see is that the stock pups do have a preamp built in to your control setup, and you will probably need to do something fancy with your switches to bypass that stuff for the humbucker. The good news is that the separate mini-toggles should make that fairly easy to do.[/font]