Where are printer drivers stored in OS 10.8?

I am trying to set up a Epson Stylus Photo R3000 as a new printer on OS 10.8. The printer setup locates the printer and automatically selects Epson Stylus R3000 with the notation "The selected printer software is available from Apple. Click Add to download and add this printer." However, clicking on Add leads eventually to an error message: "Can't install the software for the EPSON Epson Stylus Photo R3000 because it is not currently available fromthe Software Update server." This result blocks me from setting up the printer.

I know the driver is part of the Epson driver software package that is installed with OS 10.8. I would like to select it manually. My question is where are printer drivers stored? How do I select a driver?

Thanks in advance!