Matricies are the devil.
Either way, when exploring level design options, you're going to have to forget ever starthing you already know and learn everything from scratch.
Cshop is good, and duh, it's compatible with dbp, but it's something you'll have to take time to learn, because level design is filled with unusual and arbitrary concepts.
If you want a matrix editor, use magic world. It's the best out there.
You could also try Milkshape and Gmax, or Valve Hammer editor for .bsp maps. If you want your level to be BSP (which is what half life uses, and what half-life 2 will use), then Hammer is the only way to go. No matter what program you use, (and you're going to have to use a program), you're entering completely new territory.
Every program listed here is compatible with dbp.
But the problem is picking the best one. I myself use 3ds max, which I only can because I have a few years exprience with the program. It's difficult stuff.