I have not seen a RPTV or DLP/LCOS set that gives as good PQ as a good plasma display...yet. At ten feet viewing distance, you'll probably want/need a 50" display. At a $4K budget, you're a little short on $$. JMHO
I was in the exact same boat with a Sony 34XBR. My choice was the Hitachi Director series 57X500. Anyway, my suggestion for your case is to get at least a 65 inch set. Either the Mitsubishi Diamond 65813 (includes 9 inch guns), and HD tuner. Or the Hitachi Director series 65X500 should be on your list. However, if you want to save some money, and don't need an HD tuner, the 57X500, plus professional calibration, can be had for around 3k and will knock your socks off. The only problem is there are only around 40-50 authorized Hitachi Director series dealers in the US.