DIY Speaker Kits, a good idea?

Building a really solid box seems to be a big chunk of the cost of some expensive speakers and there's cheap stuff at Home Depot and Menards that anyone could use to do this.  If you attached a porcelain floor tile to MDF it'd be near resonance free.  It'd cost next to nothing.

The key to having some resale is to pick a very good model to build from a well known vendor. If you go with something too obscure then there's a limited number of people following the design or vendor and without a following..tougher resale. 

I have the CSS 1TDX and 2TDX.  They were fun to build and sound awesome.  When you build something yourself, you have an extra attachment to it.  And the price to performance ratio is very high.

I have some homemade Magicos and melting that pile of aluminum was sort of intense but totally worth it.

I'm mid-design on a pair of 2 X 6.5" 2.5-way with a ribbon/AMT tweeter. I just got fascinated by the 2.5 way design, and the more I've dug into it, the more ingenious the 2.6 way design is. It's not a 20Hz 120dB bass monster, but rather a small to medium room design good to 40 Hz. It's been fun learning all the subtleties  of crossovers, step frequencies, and a bunch more.