Datebook under GVM does do sound, except that GVM sound doesn't really work.

There's Osmo, which is a toy, and GPE, which is coming along nicely but,
as you have noticed, light on features and not completely integrated.
There's no communication with the Maemo alarm system,
so if GPE calendar isn't running, you get no alarms.

The KDE PIM suite is pretty good, speaking as someone whose life
is completely dependent on his Tungsten C and DateBook5.
Google KDE and Kontact.

At the moment, you have to install all of KDE to get it on your Nokia,
which is a fair bit of hoo ha, and the performance is sluggish.
But it does work, and there are other people here using it.

There is a stand-alone version, kdepimpi (for platform independent)
that some people are working on porting. Search the forum and encourage them.

My hope is that that will be the one that will let me leave my Palm home.