I would start with a 155 (since you're looking at Spec' line), or generally something 150'ish. 143 sounds too narrow, and yeah, what you're riding is definitely too narrow for you.

The good news is that you're obviously sitting well far back on that saddle, and you haven't described any butt-crease issues, so the shape of it seems to be working well for you. It does look pretty T-shaped from the pictures, so Specialized saddles are probably a good place to start.