I fully understand your point. Speaker building is not a wife friendly hobby. It can be very messy, and especially in this hot weather, it can get extremely frustrating. Every time i build a speaker, i swear to myself that i'm not building another one, but then after a few months, i go right back to building my next last one!
It'd sure help if i owned a table saw and some semblance of dust collection. Its been a while since we've parked our cars in the garage.
As for why most speakers are made of MDF, the reasons i can think of are:
- Lower cost
- Easy to machine
- structurally consistent
But the main disadvantage as far as i'm concerned is the fine dust. Chips from plywood tend to drop down, and are much easier to clean up later. And also the MDF cabinets can get quite heavy. I don't mind the weight as much as the dust that flies everywhere. Its extremely difficult to clean up afterwards. But if you can get the MDF cut someplace else, you should be able to put them together in your garage with minimum mess. Like i said earlier, these cabinets are fairly straight forward to cut and glue up.
That being said, i've not heard the tritrix which have received some good reviews. But i'm willing to bet that the ER18 MTM will beat it handily (and at 4x the cost, it better!). Irrespective of what you decide to build, i wish you the very best of luck.