You've got a solid game here, but there are a couple flaws. I'd like to hit a few points.
First and foremost, it feels like I have to rely far too much on luck. This is a strategy defense game. I don't want my strategy to fail because I didn't see a mana potion in two waves. I don't want my strategy to be irrelevant because I got 400 extra gold in the first 2 waves so I just steamrolled.. There should be more reliability than what we're working with.
Secondly, WOW upgraded towers are powerful. This feels -really- good, but the enemy needs to be tougher to match. The boss fights scaled appropriately, but the entire second half a map's waves are completely outclassed and inconsequential.
Third, Amazons. They are incredibly frustrating to see in numbers. I would suggest spreading them one or two in the van or middle of a wave to sow controlled chaos with Charm as is. Other options are to severely reduce its duration, or make Terror grant a tower brief immunity as well as breaking it. Maybe you could even preemptively use it as a buffer. Whatever the solution, the problem is Amazons are the wrong kind of hard.
Lastly there was a static crackle in the music track. That'd be a wonderful thing to be rid of.
There's a lot good going on here. A little polish would make it great.