so I'm getting a spider valve MKII HD100 soon and i was wondering if it interacted with the line six M13? Because im not going to run an RP350 through a tube Amp
im not quite sure what you mean, but there will be no magics happening between these two products. im quite sure.
You can plug your guitar into the M13 and run that into the input on the Mk II HD 100. It will act just like any other pedal in that respect. It should work fine.