Dan,
As far as I know, from research and personal experience, your Pia grapes are central california valley grapes that just won't provide the flavour and body you're after. I think they are a great value (at least at the prices we get them for here in Calgary) but they aren't going to make an epic wine.
The only thing I can think of to try is to draw off a significant amount of free run juice after crush, effectively boosting the skin/juice ratio for the rest. The side effects is that you get less wine and a higher cost/bottle, and likely higher tannin levels. The Pia Cab Sauv I've done was never terribly tannic anyhow so I wouldn't worry too much, and if it gets too tannic by the time it's nearly dry you could decide to try an extended maceration. I'm trying this just a bit with my Syrah this year, but unfortunately don't have a "control" batch done the normal way to compare...
The obvious choice though for better wine is to find better grapes. Unfortunately that takes a lot more effort than finding central valley grapes, and the cost seems to jump quite a bit.
Cheers, Richard