Yeah, personally for me, 40" is just fine from 2m. If you're predominantly going to be watching SD DSTV channels, theres little point is stretching the same 720x576 pixels across another 6" or 11".
Depends on how finicky you are about PQ/motion clarity, but I would go to a store that has the D6000 (LED/200Hz) & the D550 (LCD/50Hz) near each other to see if the D6000 really provides a tangible/noticable improvement for you (PQ/motion/3D etc). If not I'd get the D550 and spend the diff on a HDPVR2P, which provides a much crisper SD DSTV picture over HDMI (+ bonus of HD channels if you have a premium sub).
I bought the TV, and I am generally very happy with it. The size is also perfect for me.
HD content is great, even SABC via Aerial is not too bad. Worst pic quality is atm from my DSTV decoder (although its German bouquet only, that is why I have to watch SABC via Aerial connection). The decoder is connected through RCA to my Amp (no HDMI!) and the output is connected to the TV through the RCA cable.
Is the pic quality that much better through the HD PVR, maybe even close to a 720p quality? I won't be watching HD TV for a while, at least as long as the German bouquet is not in HD