First, a sashimi knife is typically going to be a yanagi:http://www.chefknivestogo.com/doiblstya30e.html
A very nice example of one.
This is a knife breed in and of itself. It's single beveled for right handed cutters and hollow backed. It CANNOT be sharpened with an EdgePro. Basic sharpening on them with a couple of stones is pretty easy.....but you can get pretty advanced with their sharpening procedures.
So if you want a traditional sushi knife....get a yanagi and learn to use it and sharpen it correctly.
If you want more information about these types of knives....please ask.....for now I'll leave it at that.
As to a more traditional western set of knives.....
Most chef's and home cooks use a chef's knife (gyuto) for almost all prep work.
A paring knife is used for small, intricate work
A slicer is used for just that
A bread knife....well, for bread
Those four knives could get any aspiring chef by.
Most, me included, will recommend you blow 1/2 or more of your budget on the chef's knife as it's by far the most used.
You've got a $500 budget....so allow $250 for the chef's/gyuto:
Here's a great knife:http://www.chefknivestogo.com/ic24gy.html
A great paring knife:http://www.chefknivestogo.com/kepakn31.html
A good bread knife:http://www.chefknivestogo.com/toitkbrkn.html
And a good suji/slicer:http://www.chefknivestogo.com/fufkmsu27.html