Did you purchase the printer new, and is it on warranty? Using a third party ink will void it.
If you're off warranty, you can save some money but since you are a photographer, I'd assume you are concerned about the quality of your prints. Once you go away from factory supplies, you need either a way to profile your ink and media combination, or a supplier who can give you a canned profile. It's very unlikely that the third party ink will print exactly the same as the OEM ink.
If you decide to go the third party ink route, make sure that the new ink is compatible with the old, and make sure the new supplier will stand behind that statement. It's not uncommon to have a lot of problems with nozzle clogs because of an interaction between the old and the new inks. If you are a high volume user, you might consider a bulk ink supply to cut your costs. If you are an occasional printer, stick with the OEM, it will save you problems in the long run.
I have had mixed success with third party inks, and can recommend one that I am running in my Roland FJ500, which is basically a big Epson. I've had it in for over a year, and it's better that the Roland ink ever was. It's called lumichrome, distributed by a company called the Digital Group in Boca Raton, FL. I'm not sure that they make a cartridge for the 2000p, but you can contact Steve Bernstein at 954-444-4382 to inquire.
****Important note*****
I do consulting work for their parent company, The Cartolith Group, and wanted to make sure you knew that I have a business relationship with them.
That said, I've also been a customer of Steve's for four years, and definitely recommend him as a great supplier.
