I also noticed a noticeable difference in the sound and video. While 10% of the cost of the receiver may be too little, I think of it as 10% of the whole setup; so figuring in the cost of everything that's plugged into it, it made sense to me. I bought it mostly for surge protection (I live in an older house), but the line conditioning did make a difference as well.

Do you need the Monster 2500? No. Do you need surge protection, yes. I work on computers for a living, and I have seen systems getting fried during electrical storms (yes I told them to turn the computers off, but they didn't listen). In short, the surge protection is more peace-of-mind than anything else, but do you really need the extra worry?

You can buy a good surge protected power bar for about $20 at your local computer store. Buy one that has attached equipment warrantee and send in the card. You never know when the next thunder storm is going to fry your equipment. If you really want the guy off your back, tell him you already have one. If you find out later that you do need it then buy one online for a whole lot less.