This one works for me.
Audio Manager also works for me and was the first application I used. I found that system volume was at level 2 out of 7 and it was almost as if the system volume setting is hidden within ICS actual settings.
However, even after setting it to 7/7; it still wasn't loud enough. This is why I installed Volume+ as above.
I had to get the paid version because it seemed like the free one didn't make any noticeable effect in the ringtone volume for me on my GNexus. I've currently got it set at 9 on Volume+ and that finally seems to have made it loud enough for me (but I still have to crank the phone's volume almost to the max to have it loud enough to hear in noisy areas).