one amp will do the trick when the panel and sub posts are jumpered (they come with brass jumpers installed), but using seperate amps for each will relieve the treble amp of the strain of driving the bass woofers, which, in the vista are passive, i THINK - double check that.
a quick check of the specs on the yba 2 makes me think it would be more than enough to handle driving both the panels and the woofers at normal levels, but 1) i don't know if it's stable into lower impedences and 2) i have no idea how it would sound with the vistas or any other speaker.... it's power ratings are plenty, though.
