Ego is a big thing why you are seeing so many big dobs being built. When the guys that built them get them done, they really do enjoy them for the views of the sky that they get and for the egoboo that they get showing them off. It`s kind of natural.
As far a doing small refractors, you really don`t get that much for your work on a little 2" or 3" refractor. The increase in the light gathering, while a lot more than the naked eye, isn`t that great when compared to larger scopes - the whole reason for Aperture Fever as it is called.
I have a 200" refractor (go to the RTMC website and look at the Merit Award winners for 1998) and while it is an impressive instrument in it`s own right, with the 4.25" aperture, it just isn`t all that much.
As far as scopes are concerned, I am getting the glass together to make a 12" F1? refractor and I have 2 pieces that will work for a decent scope at this time. I am looking for a third piece that will make it a surpurb 3 element scope.
Reflectors are so much easier to design (all newts are parabolic mirrors) and build than refractors as the refractors need to be raytraced with the particular glasses in mind. Go to the Schott Glass website and download thier catalog of optical glasses and be prepared to be blown away! For a good book on the designing of lenses and other optics, get the Rutten and Van VenRooij book, Telescope Optics, Evaluation and Design and the software that comes with the book. Total cost is $50 and is well worth it. It will describe optics to you so well that you will become an instant expert to your friends about all things optical. On some of the lesser known designs, it doesn`t go into much detail but most designs known at the time are mentioned to some degree or another.
P.S. congrats on getting into the hobby without spending a lot of money. That 4.5" scope will provide a lot of fun and with skills at grinding and polishing glass and making mounts for that glass, you will enjoy without spending a lot of money on things. You will also want to learn what a Crayford focuser is and when you do, you will want to build them for all of your scopes.