Connect. Please help


I have tube pre amp with 2 pre out. I have 2 set speakers. I have 1 stereo amp and set of mono block amp. 
Can i connect pre out 1 to mono block amp and pre out 2 to stereo amp, if i listen stereo amp I will keep the mono block OFF or listen mono block I will keep the stereo amp OFF? Thank for help
Pre Amp Unison Research Mystery 2
Mono Block  Vincent SP998
Stereo amp Parasound Halo A21
nguyen828
Here my setup, 1 room 2 set speakers (depend what music i want to listen)
Auralic Altair RCA to in Mystery Pre and out to Mono to VR4Jr. Second pre out to B&W sub( I think this setup good)
I connected another XLR out put from Auralic direct to Halo A21 to Opera Seconda . I do not like the sound without pre amp. That why i am thinking to disconnect second pre out to sub and connect to Halo, use Halo loop to B&W sub. Because i don't  think VR4jr need sub. Please help! Thanks for all advice
Merry Christmas to everyone 

Imhififan got you what you need to watch out for about the Vincent hybrids. Hopefully saves you some head scratching. I suspect your SP998 has the same design approach and may need to power it up.

Keep us posted.