To my knowledge, at this time, there are no 'hi-fi' hearing aides no.
I am fitted with Siemens Pure 301 digital aides, with in the ear speakersunits and open type domes in the ear, which helps not to cut off what freq you can still hear well.
For me it is not so much for loss of hearing - my tests are pretty much in line for my age - but for tinnitus which I got from 20 years of prednisone and several nasty aenesthetics used in operations. The HA for me produce white noise, and if I so choose amplify a little so my ears are never bored and the inner noise levels take over..
Things to avoid are ibuprofen, aspirin, etc.. It is called ototoxicity - chemicals which cause hearing loss or damage. Also ofcourse don't overindulge on loud music.. Although legal limits for workplaces etc are set around 83dB above which protection must be worn, levels lower like 70db at prolonged exposure already causes loss.
There is in the USA a company that supplies very good HA their models are called RITE if I remember corrrectly, which come with software in which you can tweak the settings yourself but extreme care must be taken. HA do amplify sounds above levels that damage healthy ears, let alone damaged ones!
Some devices come with their own interface, and others adhere to standards which means they need a separate costly device like hi-pro
http://www.diyhearingaids.com/VirtualTechnician.aspx
http://hearingaidforums.com/showthread.php?t=9840 Good information on this subject on that forum.