Reply to SCS3 as a system? Or just SCS3d with a regular mixer?

I've been looking to buy an Scs3d or two due to their portability and the amount I travel. I know a couple people here use them regularly, so I got a few questions.

Is it comfortable controlling 2 decks from one Scs.3d? Or should I invest in two?

Should I buy the whole system? Is the SCS.3m worth it/worth using? Or is it better to pair the two SCS.3ds with a regular mixer?