because of my 80s duo, in effect a silent stage, I had a behringer 205 tiny monitor. This really helped my singing, as I could monitor at a lower level.
Then came the IEM which made it better again. They've made me a much better singer to the point that I would rather sing than play bass.
As i've carried the iem into bands I play with, it has improved my bass playing as I can actually hear what I'm playing, I hit the strings not so hard which makes my playing more dynamic, as I have somewhere to go if I need more volume. My bass sounds great in my ears, more inspiring to play.
I suppose that I am lucky, the KZ fitted my ears and gave me a good working system with the P2 all in under 100 quid.
I now use the MI-Pro 58 wireless kit, which works brilliantly and sounds fab and obviously is wireless.
All brought about by a tinnitus issue that I don't want to get worse. The information on this thread, with the input of you excellent Basschatters has changed my world and if I win the lottery, I'll send you a few sheckles