A line drop amp does work very well. It works like the signal booster above but also does have filtering.
I use the 2400 model.
http://www.electroline.com/en/products/drop_amplifiers/eda/index.html
I use a line conditioner because I have sometimes power fluctuations in this older apartment building. Giving steady full power to any power source keeps that power source healthy. The fluctuations is what kills em .. such high failure rates with power supplies in computers.
This is what I got:
http://www.tripplite.com/products/product.cfm?productID=211
It does not improve sound...myth...but it does keep my power steady and clean.
