Is a high priced Line Conditioner needed

Although I don't know the answer, you bring up an interesting point.

I've read that a lot of power conditioners negatively affect a system because of the filtering used.

So if that's the case, as you asked, do you need one at all? If you do, what are you needing to either condition and/or protect, and how can you do it with no or the least amount of negative effects?

Chuck

You may need a power conditioner if the power in your lines is noisy or suffers major lag periodically. I am sure the power conditioner manufactures or their devoted fans will tell you it is essential, after all -all of what we do is manipulate power.
My personal experience was one that found no benefit from power conditioning no low power drags and most importantly my dedicated lines were noise free. I think you have to ask yourself those questions. There is no mandatory audiophile rule stating that you must have power conditioners.

The Cable Company will send you some line conditioners to try first, before you buy them. I would go that route. You never know what's going to happen when you put power products in your system.