Using two amps together

Hello all, this is my first post so I thought I would ask a question that has been haunting me for a while.

I have two amplifiers that I have used at the same time with a boss splitter pedal. Now the sound I get from the marshall AVT100 is fine but the Kustom head just doesnt give me what I want, but it happens to be as loud as hell!

I am hoping there is a way to run the amps in series (if thats what its called) where the marshall amp is the one that will create the desired sound but the Kusom amp is the one that gives the volume and drives the 4x12 cab. I suppose in a way the marshall would become a sort of pre-amp and the Kustom would be where the power is produced.

I hope this makes sense.

Thanks all