[Christ]

If you're not sure about which intake to buy, just stick with the stock one. Your OE air filter is designed to flow enough air to satisfy the engine at WOT in most, if not all driving situations, so that's not even worth bothering to consider about. (This is proven, and you can do the math on your own.)

The intake piping itself, technically using smooth tubing, regardless of intake temps, will help out. It takes energy away from the air (more vacuum to move it) when it has a rough surface to travel over. It's negligible. You'll get a better result from spending $1 at the air pump to make sure your tires are inflated to spec (or sidewall max, more if you're comfortable with it.)

If you're going to put an intake on a stock Civic, do it for the sound... or for the noise... or something. You won't get any gains from it otherwise, and even if you did, it wouldn't be worth the money you'll spend.