Two separate systems one set of front speakers ?

I think I know the answer to this but maybe i don’t so seeking guidance …
I am currently running a marantz sr18 receiver and oldie but still a very good HT amp. I am running the pre out for the front to a gryphon amp to drive the front speakers - b&w 801 s3 speakers.
This had been a good setup but the line out on the marantz front pre seems to be low – which has just start to annoy me over the past 6 months - even after maxing everything out in the front channels set up - the Gryphon for straight 2 channel is at 9 for audio but for home theater around 2. I am looking for options going forward and was wondering if i took the marantz front channels and feed a separate speaker line to my speakers for Home theater and had two speaker lines (only ever have one going) one on spades and one on banana plugs - would this have any effect on the sound of my system – I am expecting not but I am seeking guidance.
Thanks Gareth
Don't do it. Even if you never make a mistake by having them both on, even an unpowered amp can load the output of the other, depending on the output stage.

Get a switch.

Dont do it, as Kal said a switch is best bet.
well there you go - I didn't think of that one - knew there had to be a reason.

thanks might of just save me a $ or 2 or maybe not - I might be in the market for a new HT amp - but shh don't tell my wife

thanks again
Niles Audio DPS-1 Amplifier/Speaker A-B Selector