Epson Stylus CX6400 (All in one: printer - scanner) setup notes:
Linux distribution: Xandros OS (Debian based Linux distribution)
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Different configuration attempts ended up in different printout quality.

The best result seem to be with using the following configuration: 
setup_printer-1.png
setup_printer-2.png
setup_printer-3.png
setup_printer-4.png in multipage mode, i.e. 2 pages printed on one page
setup_printer-5.png       "
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Using with CUPS

http://localhost:631/printers

EPSON Stylus Color Series CUPS v1.1        Description: Epson_CX6400
Location: /dev/usb/lp0
Printer State: idle, accepting jobs.
"CUPS v1.1.14 is ready to print."
Device URI: usb:/dev/usb/lp0
=================== /etc/printcap
Epson_CX6400:
=================== /etc/printcap.cups
Epson_CX6400:
=================== /etc/cups/printers.conf
# Printer configuration file for CUPS v1.1.14
# Written by cupsd on Wed 03 Dec 2003 09:22:52 PM GMT
<Printer EPSON_USB2_0_MFP>
Info CX_6400
Location /dev/usb/lp0
DeviceURI usb:/dev/usb/lp0
State Idle
Accepting Yes
JobSheets none none
QuotaPeriod 0
PageLimit 0
KLimit 0
</Printer>
<DefaultPrinter printer1>
DeviceURI parallel:/dev/lp0
State Stopped
StateMessage Paused
Accepting Yes
JobSheets none none
QuotaPeriod 0
PageLimit 0
KLimit 0
</Printer>
=================== relevant kernel modules
Module      Size   Used by
printer     6752    0
usbcore     54976   1 [printer CDCEther acm usb-storage usb-uhci hid]
=================== links
http://www.linuxprinting.org/show_printer.cgi?recnum=Epson-Stylus_CX6400