http://www.hometheaterhifi.com/volume_11...004-part-1.html

Quote:
the three walls that it does have are currently naked. Sadly, I find that I get fatigued listening to this setup very quickly.

Jack's link has the right answer - acoustic treatment. Especially the part on Page 3 that features my company's products.

Seriously, fatigue is caused by early reflections and untamed echoes and ambience. Bass traps are equally important, but a three-sided room has the advantage of less bass build-up. However, it's best if the missing side is behind you.

There's a lot of non-sales advice on my company's web site, linked under my name below. This article in particular will give you a good start:

How to Set Up a Room

Then follow up with any questions.

--Ethan

The replies regarding room treatments is correct and important speaker placement has not been brought up.
Speaker position will make a big difference in your systems sound. Typically it will create an increase in output at certain lower frequencies. These low frequency peaks can be very annoying.