We had a guy in the club many years ago who invited us over to hear his new Hsu subwoofers. After listening to the system for about 15 minutes somebody asked "Hey Lou, this sounds great, but when are you going to turn on the subs for us?" He laughed and said they were playing all along. He then he turned them off you definitely heard the missing lower octaves, but when they were turned on they just did what they needed to do and did not draw any attention to themselves. These were the original Hsu subs built with the sonotubes. From what I have been lead to believe the reason they were discontinued had nothing to do with performance but rather with shipping problems. Although the sub sounded great, too many of them got damaged in the shipping process. But if you are going to build them yourself, shipping would not be an issue.
I would suggest starting with a sonotube design. It is quick, easy and cheap to put together and if it doesn't work out for you the driver can always be pulled out and but in a different type of enclosure with not big financial loss.
