This is probably a better question to ask in the Video section.
You'll want a MIDI capable mixer so that you fader movements can be tracked by SSL for transitions, etc. Since you're using SSL and not SDJ, you'll likely have to MIDI map all the controls, but that shouldn't be a big deal. Also note, regardless of hardware, video mixing only works on channels 1 and 2.
One option for a mixer is to find a Serato DJ supported mixer as those should fit the requirements and it would allow you to try out SDJ if you wanted.