I seriously doubt any 1.8L displaced Honda will ever need to move 780cc's of fuel at anywhere below 1 bar.

Most 2.0L engines won't move 500CFM under 1bar with any turbo. Matching your injectors to whatever airflow your engine can sustain at WOT is the easiest thing you can do to help get the idle straight. Going too big can become a tuning nightmare.

2.0L DSMs come with 450cc's. Many DSMers upgrade them once they start pushing 17+ PSI. I know we're talking about Hondas here, so I'll just add that the Honda port sizes for intake and exhaust are half the size of a DSM's, and don't flow as much as a DSM can.

I'm with lkaliburn. 450's are fine. But to me, the turbo selection is waaaaay overkill. Get something smaller and cheaper. GT series are balls-to-the-wall, and unnecessary for the type of use you described.