I thought as well initially that it’s a matter of simple amplification. First of all, let me guess your hearing loss is rather mild in comparison to many. Next, the HAs you use probably do not completely occlude the ear canal. Those highs you hear, as well as the lows you hear are with or without the aids? That’s just pass through.
I did exactly what you suggest with some very expensive headphones, a computer with HD audio, and a 32 band equalizer application along with a tone generator. Got the home office nice and quiet, turned off all the audible notifications on the PC (seriously - this is a dangerous experiment - read on at your own risk).
Next, I turned up the inline volume control on the headphones all the way. I turned the computer’s audio up to full output I lowered the equilizer’s outputs to the minimum setting. (I don’t have the headphones on my head yet). I selected a 1,000 Hz tone.
I increased the gain at 1,000 Hz using the equalizer until I could hear it in the headphones without wearing them, then lowered that value by half.
Headphones on, balance to full right ear, no left ear. Did I mention this test is dangerous if you’re not careful? Adjust equalizer so I can just barely hear 1,000 Hz. repeat for other frequencies, at whatever frequency points you care about. With 32 channels, I could get pretty specific.
Repeat for left ear.
Now you have your baseline. Take the headphones off. Increase each frequency point by 30 dB. Lower the computer volume to a minimum. Play some (insert favorite piece here - hey, how about some Les Paul?).
Put the headphones on, and very slowly increase the computer’s sound output until you hear at a comfortable level.
Next forget I told you this and never do it again. Here’s why. Tap your arm. Feel it? Doesn’t hurt does it? Thump your arm in the same place. Doesn’t really hurt but kind of annoying. Now have a bunch of alcohol so you won’t really feel anything and whack your arm with a hammer. Didn’t hurt because you’re lit and feel no pain. Bruised the heck out of your arm didn’t it? Hit it harder until you feel it.
The hammer scenario is what happens with simple amplification. I have to hit my eardrums (with sound) really hard to make myself hear 4,000 - 6,000 Hz. I have about 90 dB loss at those frequencies. I’m damaging my remaining hearing by increasing the sound pressure at those freqs.