Most moderate or better receivers will allow you to boost those frequency ranges where you might have deficits. I, for example, have a little trouble with the voice mid-range frequencies, and have boosted both the mid-range and center speaker output for improved clarity.
If you get a HTIB, make sure that there is an equalizer where you can boost selected frequencies.
On your present TV, if you have both bass and treble controls, try turning down the bass, increasing the treble and overall volume.
Between getting old, the whine of the helicopter turbine engines, the mini guns and to many grateful dead concerts, my top end frequency hearing is shot. The voice on HD TV is not clear enough and I have to cranking up the volume to much to hear the dialog clearly.
I'm not looking to spend a lot of money on a sound system but am thinking a basic HTIB might allow me to adjust for this problem.
Any suggestions would greatly be appreciated.