There are a variety of issues here hgregs. First of all, the reason the crossovers are in the cabinet is to protect the high frequency speakers from low frequency energy. A horn type tweeter will die a quick death when subjected to high energy low frequency. The reason we crossover into the low frequency drivers is so we don't waste HF energy into a driver that cannot reproduce it, or reproduces it poorly.
So, any full range box can have it's low frequency and high frequency drivers disconnected from the crossover and tapped out via 1/4 connectors on the back of the box. If the HF side has more than one driver you need to determine how the crossover works. If you are looking at a 410 cab with tweeter I see almost nothing to be gained by biamping. If you are going to run a pair of 15 on the low box and 2 or 4 10 in the high box, just use the biamp crossover to send everything below about 400 or 500 hz to the 15's and leave the 10's box alone letting it see 400 and up. If you are buying a box with one 15 and one tweeter, you are almost doomed to kill the tweeter because the internal crossover will have been designed to limit the energy going to the tweeter. You can try, but just remember to keep that channel REALLY low until you are balanced. Or, reverse engineer the crossover so you can keep it's power limiting intact and make connection to the tweeter through the high side of the crossover.
So, you must provide a way of isolating the Hf and Lf before it is amplified and then use separate amplifiers for each frequency set or one channel of a stereo amp for Hf and one for Lf.
Let us know what equipment you are going to use and it can become clearer.
Dan
Alembic makes a device called the F1-X that provides this for you. It also has a tube driven front end, tone control. and an effects loop for reverb or other line level effects. I was unaware that the SF-2 had a crossover too. But if so it would work.
You need to study up and understand what I've just related to you before you start. It's not rocket science but it can be costly to get it wrong.