Going from 50" SXRD Rear Pro to Possibly 60" LCD: Improvement?

[Hillside Trece]

We may be in a position to somehow, someway squeeze a 60" display in our entertainment center which will replace a 50" Sony SXRD rear pro. I am going back and forth between plasma and LCD for this endeavor, and I am leaning towards LCD as I happen to like the "motion smoothing"/frame interpolation features of these sets if used in moderation (the way it makes Blu-ray 1080p material look a bit more like surreal video footage).

Will we notice an improved sense of picture quality going from a rear projection set to an LCD? Will the difference definitely be noticeable? What would be the major elements we would notice off the bat -- increased picture punch, contrast, brightness...etc?

Finally, will a 60" LCD look okay viewed at a seating distance of approximately 12 feet?

Thanks in advance, everyone.