so whats the cheapest solution
Again:
IIRR Reason studios allowed you to switch which is where I came against latency with KB input - bad news
I cant go back to nerdy racks land Im cubased now
I cant see a use for an audio i/face, Im KB , no guitar, harp, external synth, indesit w/m/c or other gear.
I have decided to power up an adjacent pc/screen to run my vid tuts. Ca plane pour moi 
Hahaha!
Look at Steinberg, UAD Volt, Focusrite Scarlett, as reasonably priced options. But Iām not sure youāre seriousā¦
Good luck
Steve.