If I were you, I'd just get rid of the task killer. Android takes care of itself. These task killer programs will only make you obsessive and provide no benefit and might hinder the smooth running of your Android operating system.
Of course, lots of people will disagree with me.
Unless you consider making it faster a benefit. Some apps really should have a "quit" option, very few do. Example, why do I need Midomi running in the background taking up RAM if I'm not going to use it for a couple of days? After you've got a dozen apps like this running, the phone starts using swap RAM and gets very noticably slower, not to mention the added CPU drain from too many programs running. Closing down apps that you've run manually and that you know you don't need doesn't do any harm, it makes the phone run quicker due to having more free RAM, and in theory could improve your battery life if the apps don't handle idling well (most do, some don't).
Each to their own though. I've got EStrongs Task manager running and the majority of apps I use are ignored, but ones that are used rarely such as Midomi and Meridian go on the kill-list to free up memory after I've used them, for the same reason I don't leave iTunes running when I'm not using it. Not such an issue on my PC with 8GB RAM, but I still kill anything I'm not going to use for a while for the sake of speed.