Well, it's a tricky one to answer as it really comes to your own preferences. Personally, I couldn't stand to watch a movie without surround sound and, now I have the Blu-Ray bug, I find I don't actually really watch DVDs any more because the Blu-Ray experience is so good, watching a DVD just disappoints me!
But that's me, I know there are plenty of people out there on these forums who have changed from surround sound to standard stereo for movie watching and prefer it that way. If you're not too bothered about surround sound, then I certainly don't think you should worry about HD audio. From the sound of your wants and needs, one of the soundbars definitely sounds the way forward for you.
Also, on the price of Blu-Rays, you can now find quite a few good films at just £7 - £10 at the likes of Amazon, Play, HMV etc. At Amazon, a number of £8 - £9 movies are also in their 3 for 2 offer, meaning 3 films can be got for just £5 - £6 each in total. New releases and popular titles are generally more expensive, but leave it for a few months and they do come down or get put in the 3 for 2 offers which makes them more affordable. The trick is definitely to stay away from the high street where prices are still £20 - £30 per disc for some unknown reason.