I think 21oz and 62" is the sweet spot. I almost bought a nice Viking cue about 10 years ago when I was playing 3-4 times a week. Until the owner of the pool hall I went too, Van Phans, gave me this bit of advice.
"If your playing in a bar, pool hall or at a friends house for fun, play with a house cue. You will be forced to be better disciplined and focused. When your skills are ready for a money game (not 5,10, or 20 bucks) then get a nice cue."

Its worth noting she was a professional player for over 10 years. Her recommendation if you did want to buy that nice cue...J. pechauer.

Thanks
Blake