Are you saying that a 4:3 HD RPTV is not capable of showing the 480 (?) or 720 (?) resolution that DVDs put out? They have line doublers and allow you to use progressive scan, right? I'm not an expert on this stuff, but I gather your knowledge is second hand as well. IMO all that technical mumbo-jumbo is used to confuse consumers and make it easier to sell them overpriced crap they don't need.
A progressive scan DVD image on a 4:3, HD, 60" RPTV will look just as good, or better, as the same image on a 42" widescreen.