HELP: how do I bridge two amps into a 810classic?

[worldsnake]

newb alert...I know. I grew up a guitarist...go figure, Im getting into the bass world now and picking up new gear. This is my plan of action but Im not sure how to go about it.

I bought a SUNN spectrum 1 and I plan on buying a second one soon so I can up my power for live gigs. Ive never done this before and the people I'm playing with are giving me blank stares so any help would be appreciated.

How do I do this?

ALSO, using only 1 amp, is there a way to just use half of the 8x10 (ampeg) for home practice purposes? i.e. just using the top or bottom 4x10.

thanks!!