I helped a friend build a pair of 2Pi Towers a couple of years back. They're tower speakers, with high sensitivity drivers. The build is a rectangular box and a rear port without a tube. Just the thickness of the mdf used for their construction. A very simple crossover. And they sound dynamite. My friend had been using a pair of Technics 2 way budget bookshelf speakers he'd had since a teenager. The transition to these was staggering.
I'd built a pair of Pi horn loaded bass reflex speakers years before that are BIG and sound BIG. I use tube and solid state amps with it. High sensitivity speakers have quenched my desire for fidelity.