The CX and VX exhausts are identical. The exhaust for a DX engine is different from the CX/VX's manifold flange, all the way through the b-pipe. The catalytic converter is bolted to the exhaust manifold on the front-facing side of the motor. The DX/LX has a pipe bolted to the manifold that runs to a cat under the car.

I noticed that my flanges were all different sizes and bolt patterns between the two, and I wound up having to weld a straight pipe from the end of an 88 CRX downpipe - to the chopped-off flange of the B-pipe to get me by. I need to replace the whole exhaust from the manifold to the tailpipe with DX parts in order to make it right. I can't make the CX stuff fit, and I don't want to.

I'm sorry about what that manual told you with the VX engine. It really is only 8 valves. Take one apart. They make 92hp at the crank. The B7 makes 104 and a lot more torque... and that's without i-vtec. The 1.6L sohc vtec does have 16 valves, but it makes ~130-135hp. That would be a worthwhile swap IMO. I'd go through all the hassle for a 30% power gain if I could get one for what they're really worth.

$100 is damn cheap. I can understand that because my DX motor was free. I wen't with the low-cost alternative as well. I'm sure there's someone out there that will sell you their B7 for that.