Use of RCA Y Splitters?

Anyone had any experiences (good or bad) in using RCA Y splitters at the pre-amp output to go to two power amps?

The preamp is sending a signal out. It should not really matter what is on the receiving end. You're talking about the output end of the amps. Should have no effect on the preamp in any case.
Wouldn't you be wiring the 2 amps in parallel, and therefore, be reducing the input impedance of both amps?