Ebbiguise555 had it right saying that your input chain is extremely important.
I'm gonna have to play Devil's advocate here and disagree with Man_Unlimited and say that I don't like the Avalon compressor at all. To my ears, it just doesn't do "that thing" that I want my vocal comp to do. I'd choose an LA-2a any day.
If you're stuck with tracks that are already recorded, you could try upward expansion of the treble range with a multiband dynamics processor - so it boosts the treble when the signal is quiet (for a more "present" intimate sound) but backs off the high EQ when the singer gets loud (to avoid sounding shrill).
Try splitting your signal onto two tracks (if your software supports latency compensation), and send one of 'em thru an Aural Exciter. Turn the volume of the Excited track way down in comparison to the other track.
jasedee has a good point, too, with suggesting that you use EQ subtractively. Sounds better, and you develop better mixing habits, too.
-Hoax