How can I tell if I need more power?

I'm driving a pair of Vandy 3A's with an older Parasound DR65 (65wpc) receiver. Vandersteen recommends 100 to 200wpc for 3A's. I've considered adding a power amp while using the DR65 as a preamp (to keep the tuner), but I since can't hear any obvious lack of sound quality, and I never get close to pushing the level to clipping with 65wpc, I wonder if I'd really gain performance that would be proportional to the high expense of a good power amp. Advise from the audio sages would be welcome.