Paul,
I started off with handhelds...and soon realised that fixed are the way forward. They dont bounce around in your hands, the batteries dont run out, and the screens are bigger.
My personal (baised) view for you:
VHF - I dont have a dsc, just a std VHF (but can be upgraded later) Mine is a ICOM M140 - which I think Martin has also. It is a cracking little set. Fully waterproof, small, easy to read, loud, and just really, really solid. Paid about 150 for mine, if you look around a little. The Silva unit you mention is a good set also, this is just my personal view.
GPS/Plotter: I have the Garmin 128 fixed GPS. This is my favorite piece of kit. So easy to use, screen is big and easy to read when bouncing around. The features are a-plenty. This unit has a 'basic' plot function on it already. This is what we use to navagate Christchurch harbour in the dark. It basically tracks/plots your routes. You can then go back to them and follow the lines. As I said it is a very basic plot, but it does for what I need to use it for. I am considering a plotter for the new boat, as they are better by a long shot (but bloody expensive!) I have narrowed it down either to one of the cheaper Garmin units, or maybe the bottom end of the Navman range.
Hope this helps, as I said it is my own biased view, based on 18 months of using them, and the superb service I have had from Garmin.
happy hunting!