well, they say 6500k is the best for bias lighting, I guess it'd be the best for room lighting too, but i'm sure most ppl would view it as too blue.
I REALLY like the 4000-4200k range. I bought a few LED bulbs recently and went cheap off amazon, so most didn't have a great selection of color temps. most of my potlights are 5000k and they are good, but the 4200k bulbs I bought are perfect, they are just like opening up a window imo.
what I think you need to worry about more than color is the beam angle. the gu10's I bought were a pretty narrow angle, I have to do a bit of a lens mod to spread it out. after doing so, it did seem to raise the blacks on my f8500 more than the previous halogens did. no idea what this might be the case, maybe the filter on it is designed for a warmer color? either way, I don't like watching tv with lights on, so not a big deal, but changing to leds definitely make blacks look worse on my f8500