The CY8CKIT-001 does have a 3.3V/5.5V Power Source Switch. Check the Quick Start Guide to locate it.
PSoC 3 can be powered in many ways. One important thing to note is that Vdda must be the higest voltage in the system.
Other Vdd's can be equal or less. Vdda can be 1.8V to 5.5V
If this is unclear, I suggest you do the on demand training , here www.cypress.com/ especially 102 - Introduction to System Resources.
Hope this helps.
Thanks. Do you know if the OpAmps User Module are supplied at Vdda?
Yes, Vdda supplies the analog core regulator, which supplies the analog blocks and dedicated analog, like opamps.