I have an Epson Stylus Color 760 on a print server and printing is notably slower than in Windows. The computers on which I print to this printer have 1, 2, and 3 gigs of RAM, so I know it's not a RAM problem. If you are low on RAM, that may be contributing to your problem, but it's probably not the only reason.
The higher your quality setting in CUPS, the slower your printing will be. So to speed up printing, first make sure you aren't using any higher quality than you need. 360 dpi will print much faster than 1440, or whatever your options are.
What you might do is set up several "Epson Printers" in CUPS at various quality settings. For example, you might set up a printer called EpsonFast and use the lowest quality needed for what you're printing. Set up an EpsonBest printer with the highest quality you need. Set up EpsonUsual for a middle quality setting acceptable for most of your printing. Then you can select the printer depending on what you're printing. It's faster and easier to select among multiple instances of your Epson printer preconfigured for what your printing needs are than to modify settings every time.
I hope this helps.