RP1000 routing possibilities into Saffire 6?

This may seem silly since the RP1000 has built in USB 24 bit interface...but, I have a Saffire 6 USB which already has my MIDI(MPK25), and my JBL monitors hooked up. Would there be a problem running the RP from left output(mono),which usually goes to amp, into Saffire inputs?
Main reason for asking, is I'm disabled(bad back), so if I don't have to crawl around and switch cables, bonus! As well as the RP not having MIDI, there goes my controller! If it would work I just plug my USB in from Saffire to PC, done! If not, I have to unhook XLRs from Saffire, run into RPs XLR outputs to monitors.
I can do it just to track guitars, but I have to hook my Saffire back up, or MPK is worthless, plus it's a really good interface! Any help, would be appreciated, do not want to fry anything, just had the RP for a few days, and it kicks a**! 
Thanks sorry if confusing!

Thanks for the reply, just wanted to make sure it was OK, only 3 days old and didn't want to fry something! There is an AMP/MIXER switch at the mono out, should this be set to mixer? The Saffire I have has 2 line in/mic combo sockets with choice of Instr. or pad, and a phantom power switch. What do you think I should use Amp or mixer, and what choices do you think on the interface(instr.)?
 Thanks again!!!

Thanks again, Yep Digitech has been my choice, well since I got the GNX4 when it first came out! Love X-Edit as well, used to love Guitar World would let you download the sounds for the songs they were tabbing in that issue! Sounds like I got it figured out, still haven't tried it yet(I know), but with the way I have things set-up, should just be instead plugging my guitar into my audio interface, just Left out(mono), will let ya know when I finally get around to it, thanks again!