Linkwitz points out several good reasons for using the LM3886 chips as high-quality amps in medium-powered applications. These devices are easy to work with and the chips cost about $5. These amps are especially well suited for building self-powered speakers with active crossovers, but unfortunately, the amount of circuitry, cost, and time to design and build systems with them gets out of hand rather quickly when you start using multiple amps and complex filters.
Apexjr is selling surplus Alesis modules that have two LM3886 amplifier chips (actually one is the lower-powered LM2876, but it can be swapped for a LM3886), and the modules include some nice active filters that make 2-way, 3-way and even 4-way active speakers relatively easy. At $5, they are a steal. There is a description of the circuitry on the Apexjr Alesis page that I posted a while back on the PE discussion board. The latest version of the spreadsheet that is referenced on the Apexjr page is in the "Technical Info" section below. This section also has some reference material that might be useful in making your own mods.
I've been trying to finish off my Heathkit amp project for quite awhile, but haven't been able to spend enough time on it in the last few months. Also, I've been collecting drivers and will be making a few more self-powered speakers for my wife's school, but just haven't been able to get past the planning stages. All I've got done so far is listed in the projects section below--hopefully I'll be able to get some more completed projects soon.
Technical Info and Calculators
Projects