OK Thanks for all that, really help me a lot think of solutions. 
 
Agree with TLW.  And don't run a FOH mix though Sonar.  I'll just start from scratch and tell you my approach. I was lead guitar in a similar band last year and recorded all our live shows with a Tascam us1641 and an old Sony laptop. 
The basis of the system was the PA was the PA and the recording gear was recording gear. 
The recording are not perfect but certainly served well as demos and fun listening for the bands education. Also was handy when I had to leave and the new guitar player now has all 4 sets of material the way the band played the songs. 
 
We had a Yamaha 16 channel mixer with stereo USB out. It had 4 AUX. 
2 monitor mixes. and I used the other 2 to feed the Tascam 2 of the main vocals. 
The USB from the main mixer is just a board mix which actually was almost good enough but of course the vocals hot. 
What I did was use 2nd sets of mikes, DI boxes and Y splitters for recording. 
So the guitar amps each had mikes in front of them and Y splitters one to PA one to Recording.
The Bass player had 2 DI access points, a DI box and the back of the amp had an XLR. 
The keyboards were analog to the PA board and midi to the recording. 
The drums I put 2 CAD condensers just so in front of the kit and got a real good drum sound, that. I got lucky! 
The mixer also had sub mix busses so I managed to steal BU vocals. 
Anyhow you get the picture.
Steal what you can from the PA mixer, inserts are best , we didn't have that option.
And then double mike  or use Y splitters and DI boxes on the rest. 
 
We never got a chance to record at rehearsals but I would have just had more options with miking things We only used in ears at rehearsals, no speakers. I used regular headphones at first until I bought my In ears.