One practical consideration is that the 2 Pi towers -- or even the larger 4 Pis -- are going to be much easier to build than the Fostex-recommended horn (I assuming you're referring to the Fostex plan available at Madisound). They're just big boxes -- although to do them right, with proper bracing and finishing, you'll have plenty of opportunity to test out your woodworking skills.

FWIW, my primary system consists of Welborne Laurels driving Pi 4s. The Laurels are 300B-based and so put out more power than the S.E.X., but with 8W I can fill the house with Mahler or Wagner -- or Frank Zappa.

• FT-1600 Construction Pix