The ST200 airbox has a hose that pulls cold air in from the fender well in addition to the factory "snorkel" on the front of the car. This is on the bottom half of the airbox. The Cobb intake replaces the top half of the stock airbox and all the piping up to the turbo inlet. So, you could run the cobb intake with the bottom half of the ST200 airbox. Conceivably this would be functionally identical to an ST200/Mountune box with a crossover pipe and induction hose, but potentially cheaper, especially if you buy used. I do not have an opinion on whether or not the cone filter with the Cobb would be an improvement over a flat-panel filter of an identical medium.
I will be running a big mouth (if I can find one used) and either a Cobb setup or crossover pipe/induction hose with my ST200 airbox (depending on what I can find for cheaper). I will log data (now that that's a thing I can do).
The Cobb has the additional benefit of being plastic and less prone to heat soak, whereas the RamAir crossover is aluminum, and I would heat wrap it. Heat really seems to be the killer on these cars, next time I need to work on the turbo I'll be wrapping it in a turbo blanket. Touge Solutions (or some company with a name like that) makes one for our little baby snail.