Well first off I'd get a monster head so I'd never need to buy a new rig again, assuming you own that cab.

Next I'd say try and find one with the same Ohm rating as the cab.

After that, it's pretty much up to you. I'd search around here on UG and find what I can about different heads, pro's and con's of certain models, all that good stuff.

But really, there is no "best head" for any cab. You have to find what head is best for you.
-Fender Deluxe Active P-bass (60th anniversary)
-Peavey T-40 (1982)
-Hartke HA-3500
-Aguilar GS 2x12
-GK Backline 2x10
I would easily recommend Ampeg or Aguilar, but they both sound different. Apart from ohmage, its all sound preference.
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Jimbo Wallace of the Godlike, Archaic, But Sexy Instrument Players. PM me to join.
Thanks, I have the cash for the monster, just wondering how much a good head will set me back.