Ok most of what you want is already default what Screenshot Captor does.
Start Screenshot captor, and then here's what you would customize:
1. In options tab "General Settings", check the box marked "Start Minimized":
2. In options tab "Interface Options 1", select the "After Capture Show: Stay Minimized"
3. In options tab "Screenshot Folder and Tools", click the button to set your Screenshot Folder as "c:\snaps\"
4. In options tab "File Naming Template", in the top Default New File Name, put: %customdate%
and at bottom Custom Date Format put: %Y-%m-%d %H_%M_%S
(note you cant use : as you requested since that character should not be used in filenames so i used _)
Capture sound should be played by default (check Post-Capture Options tab), so nothing to do here.
Hotkey should already be set as you want:
Let me know if it works for you.