There are headphone amplifiers to assist in getting more out out of what you have. There's that and I see these amps on amazon, etc.
http://www.cnet.com/forums/discussions/headphones-for-hearing-impaired-277558/ goes over other things.
I need headphones for TV viewing. I am very hard of hearing. I have a set of RCA WHP141 but they are not loud enough anymore. I need to know how to tell which headphone is best. Most sellers do not give decibel ratings and I do not know what decibel would be best for me. Can anyone help?