In My Opinion, plasma is a huge upgrade in of itself from a DLP RPTV. Just my opinion, but I'm used to actually having good shadow detail now. There are many terms, scientific ones included, that I don't quite understand yet, but there are just so many cinematic scenes that have such varying levels of light within any given moment. IMO, it's just a different experience altogether.
So. Coming from a guy with a 75 sq ft display, I honestly honestly honestly would take the 65" Pana 850u over any current RPTV, even if 82".
My parents have a DLP. My brother has both a large DLP and entry level Pana plasma.
As for the stars not being aligned, I have to say that I had in mind that the FP would be the only display.
But, with the roughly 4k you're looking to spend... you could still get the following:
42" Pana 720p television $600
used JVC RS1 (that's what I have) for $2.2k
use the remainder of budget on a tab tensioned OR
a DaLite high power manual for $300 and keep nearly $1000 in the pocket
or something like that
I use RS1 with HP, and it's impossible to describe.
http://cgi.videogon.com/cgi-bin/cl.pl?projmisc&1248894979
http://cgi.videogon.com/cgi-bin/cl.pl?projmisc&1249011880
or just spend a few hundred more for a new product like Epson 6500 or Pana 3000.
So, yeah, ok, if I had 4k, and I was you, Id still go FP + small display.
If I can only choose between smaller plasma and bigger DLP, I go with smaller plasma.