I have been contemplating adding a sub to my current setup for a while. Having started looking around I am beginning to wonder if I should upgrade my main speakers instead. I currently have Mission 702 fronts and a M7C centre which are OK but I am getting a bit bored with them. If am prepared to spend £800 on a sub, would I be better off upgrading to a setup which will reach lower levels of bass than my current speakers and have one less box in the room? If I spent the £800 on better mains/centre, Is the addition of a sub really necessary? Thanks, Mike.