Is it possible to show ongoing notifications under regular notifications?
Notifications, at least in CyanogenMod or AOSP, are ordered in order or the last updated notification.

If you have an app that updates the notification, then the notification will appear on top when it updates.

There is currently no way to change this behaviour.

Note: Some stock ROMs order the notifications into ongoing etc, this is the design of the manufacturer, and can also not be changed 

You should get something like what you are asking in cyanogenmod.