Vortex Sound Research

I currently use a Scarlett 2i4. I’ve had it for years and have never had any issues. But I have a lot more hardware now. Multiple synths, drum machines, samplers fx etc.

My question is : Would I be better off getting a new interface with more input channels or an analog mixer to run all the hardware into then just run that into the 2i4 inputs (stereo)

I want to buy either a new Scarlett 18i8 or a Soundcraft epm8.

Any suggestions or knowledge greatly appreciated. Thanks.