Funny you should end up here! I think Wayne's loudspeakers are the best way to get high quality high efficiency sound for the money! You can pay more for greater refinement but for simple designs that are relatively easy to build and don't break the bank you can't beat them. Other approaches to Hi-Eff. such as Fostex back-loaded horns and for more $$, Lowther B.L.H.s, though sounding very good are to a greater or lesser extent not really full-range systems IMHO. At our New England Bottlehead meetings, whenever "Real" speakers such as the Theater 4s are present, they are always the choice for extended listening after the other more modest homemade speakers are given a chance to play. The only downside is their up-side: They can be fairly large. I don't take my Theater 4s out of the house! But boy do they make music with my Paramours and I'm sure they'd do great with 1.5W. These speakers are a joy to own if you are a DIY type since subtle changes in the electronics are distinctly audible through them. But tweakers neurosis is a deadly disease and has ruined many a marriage and resulted in severe reprimands from employers for tardiness!
I'm not sure how loud the Studio 2 Pis would go with the SEX amps but they'd be at least as loud as the pipes you were considering w/1534s and would be more refined sounding(just a crude guess). Even so, I'd go with the Theater 4s if you can swing it!

Good luck!

Garland