I hope you're only talking about exhaust manifolds.

Extrude honing has fallen out of favor. The results aren't worth the price. I'm guessing a cost of between $50 and $100 per horsepower. https://boneheadperformance.com/extrude-honing/extrude-hone-pricing/
As famous engine builder Joe Sherman said, "It is a total big waste of money==TOO BAD".

Increasing flow in the cylinder head allows one to use a smaller camshaft for the same power. Getting air into the engine is more difficult than getting it out because less pressure available to push it in than to push it out. So good heads will always help.

Making the engine bigger may not increase the horsepower if the engine is flow-limited, but it does move the torque curve down the rpm scale and thus the vehicle feels much stronger. So for a street driven vehicle, assuming you can get grip, the larger engine will always feel more powerful. Alternately, you can decrease the gear ratio and keep the vehicle feeling the same.

R.