I agree with what the guys above said. The reason you drink mostly Cab is because there's so much of it around Napa and Sonoma. In Napa, it would be dumb to plant something for which you would get half the price or less. Sonoma is not so much locked into Cab, so my suggestion is to look around Sonoma.
Napa does have other varieties, it's just that prime land goes to Cab and that's what people think about. But you like big wines, so look for Petite Sirah. There is some in Napa. And Syrah, there's some in Napa as well, but more and more interesting in Sonoma.
And you don't have to drink single grapes. As mentioned, there's a lot of great wine coming out of France, Spain, and elsewhere. Tonight I had a wine from Toro. If you like big Cab and Zin, it's something you'd likely enjoy but it was a fraction of what you'd pay out of Napa.
Anyway, good luck on your explorations!