set speakers large or small?

To expound a bit further - for all you 2 channel audiophile purists and full range stereo speaker devotees - yes, you're going to certainly get more perfect coherence running a full range speaker system, full range (and maybe adding minimal subwoofer integration to the very bottom registers, .1 configuration, etc, for home theater). A main trade off's here includes getting coherent full range integration of the sound, but most always yields limited dynamics and impact from the system, from relying on typically dynamically limited passive speaker systems to provide the weight and authority to the overall sound. You cross things over with bass management, to an active woofer in the system, and the efficiency and power just went up! You get higher efficiency speakers, and or even active speakers on the top end, and you have even more dynamic range and impact potential!
Of course, again, integrating a separate woofer speaker with your mains, and you will face a trade off of perfect driver to driver integration, from crossover issues, phase, slope, whatever. Still, the trade-offs here - for most all multi-channel/ht applications, far out-weigh the negatives!
Anyway, opinions will vary. But every multi-channel, full range, passive speaker system I've ever heard lacks proper dynamics and impact, compared to integrating an active woofer in the chain - at the very least.

I concur with pretty much everything Queefee wrote, but add this cautionary caveat to his Pertinent Quotes: Just because AE was a brilliant physicist does not imply he was a brilliant philosopher. There are many things I'd rather know through reading, secondary observation, or generalization rather than direct experience.

Palen, the THX rationale is based on the contention that we are not well able to localize frequencies below 80 Hz, a contention I contend that is based on psychoacoustic evidence.

db

wow,a lot to take in,i did use a spl meter to set it up but my room is a little strange i think the best thing i can do is try differant settings and move my speakers around a bit,not much room for movement and cannot move sub at all.i would like to thank you all even though a lot of it was over my head

Set your front mains to large. Your center channel to large if you can, but try it in both to see what works best for your room. The LFE channel in movies is separate from the bass information that is routed to the individual speakers, so you aren't robbing from your sub by setting individual speakers to large. I have my Focal 826V mains set to large and the movie/concert watching experience is much more visceral that way.