Glen... the point of diminishing returns is somewhere between 25" to 32".
If you want more aperture than that, get a pair of primaries and make a binocular. You could always do that with your current scope (buy another 16" from GSO) It will have a similar limiting magnitude as a 19.2" but the aesthetics of the view will be in a completely different league (better).
Go here:
http://www.binoscope.co.nz/birth.htm
I would strongly advise against a 1m f3 ... don't even think about it, it is a really really bad idea.
As for the telescope structure... build it yourself, it really isn't that hard.
If you want someone else to build it, Peter Read would be top of the list, Webster also makes a fine telescope, and Obsessions are pretty hard to criticise in any way I can think of.
c