It's not the prettiest-looking sound bar, but for $400 there's nothing that sounds as good as the Pioneer SP-SB23W. The included subwoofer is tiny and wireless, plus there's built-in Bluetooth for wireless audio streaming.
Just because you're going for a sound bar doesn't mean you can't have real surround sound. The Vizio S4251W adds two surround speakers to the standard sound bar design, letting you get true surround sound without the hassle of a more elaborate system.
The SpeakerCraft CS3 is on the pricier side, but it offers up excellent sound quality in a very sleek design. There's built-in Bluetooth, plus it makes a decent amount of bass without requiring a subwoofer.
For a budget sound bar, it's hard to beat the Sony HT-CT260. It has a striking design that fits well with modern TVS, plus there's a built-in IR repeater on the back in case the sound bar blocks your TV remote.