Groundplane in poweramplifier PCB design

Hi,

I've just about finished designing a PCB for a HiFi power amplifier, and now
I'm wondering something. Is it a good idea to fill up the unused space on the
board with ground copper (without orphans of course)? Or, is it best to keep
the ground clear of as much parts as possible, as you do with the supply
lines?

The speaker returns go directly to the main power supply BTW, so the
groundplane is not necessary for that.

Thanks in advance,

Wiebe Cazemier
.