Thank you in advance for answering my question.

Since I am new to this, I would like to know do I really need have additional amplifier? or the existing setup is ok?

Here is my setup
Home Theater 6.1
AV Receiver - Denon 1908
Front Sides - M60 V2
Central Speaker - VP100 V2
Subwoofer - HSU STF-2
Rear Sorround - Speakercraft AIM7 TWO (3 Ceiling Speakers)
+
Zone 2 - Whole house Audio
3 rooms home audio (total 6 Ceiling speakers)
All are Speakercraft AIM7 TWO ceiling speaker
with Speakercraft VSI60 Vol Ctrl (Impedence Matching)
with Speakercraft SWTS-4500 Speaker Selector