it is correct, though most mono amps have built in cross overs...they are usually defeatable though. It is a better way to go if cost is not an issue as it allows maximum flexibility in components, and adjustability(tuning). Bazooka tubes are a nice addition to a simple system, oem, or for a very specific application which requires quick access to areas below or behind the sub. As I've said, I think they sound very good, and are very convenient, easy to handle, and relatively cheap...but if I'm looking for performance...big box and big subs with lots of power!

 

I just want to clarify that it is perfectly fine to use the sub crossover in the deck even though the one in the tube is not defeatable - especially considering the one in the tube is preset so high. Is it ideal? no. Will you notice it? doubtful.