Just got new IMac and loaded SC3. Printing on Epson 2400. Only way it will print is "High Speed" and can't find control to turn high speed off. Used windows before and had no trouble.
It's at the bottom of the print settings view, right below the print quality dropdown.
I assume you've already discovered how to show the full print dialog (with the big blue disclosure button next to the printer name)?
If it's not there, you may want to try deleting and re-adding the printer from System Preferences. The Epson driver should take over once it's been installed, but occasionally people run into a problem where the universal driver remains in use.