I have a 65 inch. I'm personally waiting for the 54inch Vizio. It supposed to support dts/Dolby, hdmi and have a full 5.1 wireless configuration. I want a full surround experience without the running of cables so this is a fit for me. Still awaiting it's release in next couple weeks.
I'm no expert here on sizes. But its not a big concern far as I'm concerned. The quality of sound is more of concern. Pioneer, Yamaha, Sony make some good sound bars that should fit your bill.
Thanks again for the input. I'll keep my eyes and ears open for the Vizio model you mentioned. In the meantime, I'll poke around at what the other makers you mentioned have to offer.
If you have previous experience with soundbars, would you say they do a decent job of at least imitating the surround-sound experience?