Sound bar for Dialogue

What is the best sound bar priced less than $500 that will help to understand dialogue on tv shows.  We have to frequently use closed captions to get the words on some shows.  I do not have such trouble understanding words on my audio system which is in another room.  Thanks.
You're not likely going to find something like this.  It could very well be that your room needs acoustic treatments.  Try putting sound absorbing panels on the front side walls.  The sound reflections can easily cause vocals from the sound bar to be extremely hard to understand.
I use ZVOX and it is so much better than the TV’s built in speakers. The ZVOX has multiple tone controls including those for bringing forward the ’speaking’ range’. They have multiple models and are inexpensive.
Thanks, Newbee.  Can you elaborate on the best model for dialogue, or are all ZVOX models great for dialogue?  I am using bookshelf speakers which are an improvement, but still some programs have dialogue that is less than clear at times.
Thanks, auxinput.  Given that my tv is in the living room in an entertainment center, acoustics could be the problem.  But wife acceptance factor does enter in.  
Sound absorbing panels worked best for me. The more drivers you have, the harder it will be to get the clarity you desire.
I always agree with having appropriate room treatment as being essential for clarity and tonal balance.

Still, I think having a sound bar is such a great feature to simplify a high system which shares space with the TV.
rdoc, The Zvox I referred to was not incorporated into my 2 channel audio system which I use exclusively for music. I only use the Zvox for TV (in different rooms) and it replaces the 'full range' (haha) speakers in the TV. Great for what it does but I doubt that it would be better than properly driven audio speakers. Re different models, size = bass performance. 
I also use the ZVOX for dialogue on my Samsung TV.  It made a world of difference as I can now hear what people are saying without having to raise the volume.  Mine is at least 8 years old, cost was around $160.00. It sounds better than any sound bar I heard at the time.   It also does bass quite well. 

I keep my 2 channel stereo system completely separate.   I only watch 5 hours of TV weekly at the most. 
I was doing research on these a while back, and the Yamaha YAS-209 got nice reviews and even comes with a subwoofer that’ll likely inject a little more fun into your normal TV experience, and it’s only $299.  Best of luck. 
Hi OP,  Just last night my wife asked why is it so hard to hear the voices?
I realized that we were listening through the Samsung TV and not our soundbar!
While I have a fairly high end two channel system, it is in another room.
I tried an inexpensive (Yamaha) self powered soundbar but it was not good to me.
So I purchased a slimline  Marantz 5 channel AVR (under 500) and a def tech soundbar (about 500) from Safe and Sound, which always has closeouts on such stuff.  It is true 5 channel, and their least expensive AVR is plenty for the unpowered soundbar.
Vocals are clear as a bell, and while not 'true surround 'with speakers behind you, it is fine for me, being an Audio guy and not a movie nut.
There was just recently a Marantz 1509 on this sight for 299.
I believe a non powered soundbar with separate AVR is the way to go.

Hope this helps,
Just plug in some decent powered computer speakers instead of the god awful flat screen audio.
I have an AVR with ESLs and a ribbon center that I never need to fire up for TV.

I highly recommend SONOS surround bar. I have been a long time user (15 plus years), very reliable and high quality sound. Easy to setup, give it a try in your home.
Center channel speakers are best for obtaining dialogue clarity.  What are you using to transmit audio?  Does your gear have the capability to integrate a center channel?
Thanks to all who made suggestions.  I was able to pick up an open box ZVOX SB500 for $150 off.  My wife and I watched a program last night that for which we previously had to turn on captions to understand a fair amount  of the dialogue.  With the ZVOX sound bar, we could understand 99% of the dialogue with no captions.  It is a great product.  In visiting with a very knowledgeable Best Buy rep, he said that the ZVOX is one of the best maybe because they make hearing aids. Thanks again.  
I augmented a pair of KEF Reference 1s with a KEF Reference 204/2C center speaker for dialog. My setup integrates an Ayre stereo preamp with a Bryston SP3 processor for surround. Last night I set the center speaker to none in the SP3 menu and was surprised by how much clearer the dialog and centered image became. I’ll try some tweaking and careful level matching before abandoning the 3.5’ wide 80 pound 204/2C.