The Behringer mini-mixers are excellent value for money, although the line outputs aren't balanced (the Folio outputs are). A DI box soon gets around that problem, and is still the cheap option.

Alternatively, keep the mini-mixer with the main mixer, though you will need to run more cables!

The Behringer has proper LED ladders, but the Folio just has peak LED's to tell you you've already gone too far! Swings and roundabouts... but you can buy two (or even three) Behringers for the price of a Folio...

It's unlikely that you'd notice the sound degradation if you aren't recording. For PA purposes it's perfectly acceptable practice - just be careful not to overdrive the input stages, though, and beware of earth loops. Try to drive the mini-mixer output hard, and attenuate it at the main mixer - it helps with the signal-to-noise ratio.