I have a significant hearing loss (otosclerosis) which can be overcome via amplification. For some years I had been using the Boostaro (old one, not the new Revolution) to good effect. When I recently migrated from CD players to the Sansa Clip, I found that the included headphones were so good that I didn’t need an amplifier with them. However, they were uncomfortable and only worked if precisely situated in my ears. I searched online and found that the Philips SHE5910 was recommended as being very loud. I got a set and they are great. With some sources, I can even reduce the Clip volume to less than top setting. Two drawbacks to them are that they have unequal-length cords to the left and right sides. Apparently they expect you to drape the longer cord over your neck behind your head. This is somewhat annoying but works OK. Other is that they are in-the-hear sets (not buds) and are fairly large. They are comfortable for me, but not for some. One poster said (quite correctly) to put a AAA battery in your ear - if it fits, then the 59810s will be OK. So you may want to try other headphones, before committing to an amp.
Re amps, the Boostaroo is $25 at Radio Shack and works OK. Mine now has a bad cord connection (after 4 years of heavy use) and I tried the FiiO which is available on eBay (http://cgi.ebay.com/Headphone-Amplifier-AMP-Earphone-Portable-mp3-mp4-mini\_W0QQitemZ380043989665QQcmdZViewItem). This works about as well as the Boostaroo, with the earphones, and is much smaller. However, I also use the Boostaroo for input to radios (for some reason, plugging in Clip directly doesn’t work well). On these, the FiiO produces a buzzy, staticky sound which is annoying.
There is another portable amp from Little Dot Micro which is also available on eBay (http://cgi.ebay.com/Portable-audio-and-earphone-Amplifier-Little-Dot-Micro\_W0QQitemZ110242700917QQihZ001QQcategoryZ3702QQrdZ1QQssPageNameZWD1VQQcmdZViewItemQQ\_trksidZp1638Q2em118Q2el124), but I haven’t tried it yet.
Anyway, good luck with this, whatever you decide. (Also, not to get too personal, but you may want to have your ears checked. My hearing had been deteriorating for some time, but so gradually that I was not aware of it as such. I only found out because I also had tinnitus (ringing in my ears) and went to the doctor for that.)
Also, thanks to those who posted re MP3 Gain. I will give that a try.
