I'm a big fan of Furuno souders and I think Garmin leads the industry in GPS, but I've made charts for Garmin and never really liked their interface. For the budget you are considering check out NAVMAN/Northstars products. Their Explorer plotter series offer quite a bang for the buck and they have excellent warranty and post warranty service ($99 for out of warranty repairs). Very user friendly and all are compatible with their digital fuel flow meters and Smartcraft if your running an Optimax. Some have integrated sounders like mod 657
Their fishfinders are quite good - just get a dual frequency like the mod. 457. Pricing might actually be reverse of your expectation (plotter being less than sounder) as popularity of GPS units has really brought their prices down.
Coastal maps that come standard with most units are fine for having a good idea of where you are but will be next to useless for for navigating tricky channels or pea soup fog, or staying on the edge of your favorite ledge. Good regional or local maps usually run about $180 for a c-map or navioncs card and due to the number of boaters in the Sound you may find a more local card for $90 or so. Check out these sites to get an idea of what's available:
www.getfeetwet.com
www.turtlemarine.com
www.thegpsstore.com
Most of these shops will put west marines price matching policy to the test
Just my 2 bits... Good Luck Gillie