Is This A Worthwhile Upgrade?

[gvatty]

I am looking for new towers and a center channel for my 7.1 HT which is used exclusively for movies. I have a Onkyo 804 receiver and a Klipsch Synergy 10" subwoofer. My room is 15'x 16' x 8'.

My current towers are Sony SS-MF550H with specs of:
Bass Driver(s)
Yes (Enhanced H.O.P. Cone)
Nano Fine® Balanced Dome Tweeter
Yes
8" Improved H.O.P. Cone
Bass Driver
3 1/4" Improved H.O.P. Cone
Mid Driver
1" Nano-Fine® Balanced Dome Tweeter :
Speaker
Frequency Response
45Hz - 50kHz
Impedance
8 Ohms
Mid Range Size(s)
3" (8 cm)
Power Requirements (Subwoofer)
40 - 50,000 Hz
Sensitivity
88 dB

My center channel is a Sony SS-CN5000 with specs of:
Bass Driver(s)
Yes (Enhanced HOP Dual 5 1/4" Drivers with 1" Tweeter)
Nano Fine® Balanced Dome Tweeter
Yes (rated to 50 kHz)
Speaker
Frequency Response
85 - 50,000 Hz
Impedance
8 Ohms
Sensitivity
89 dB
Tweeter Size
1" (2.5 cm)
Woofer Size(s)
5 1/4" (13cm) x 2

I'm considering replacing the towers with Polk Monitor 50s with specs of:
Driver Units Mid/Woofer: 2 - 5-1/4" Diameter (13.34cm), Dynamic Balance Bi-laminate composite cone driver, magnetically shielded
Tweeter: 1 - 1" Diameter (2.54cm), Dynamic Balance Silk/polymer composite dome, magnetically shielded
Power Rating 20 - 150 w/channel
Frequency Response 42Hz - 25kHz
Nominal Impedance 8 ohms
Sensitivity 89 dB

A polk center channel CS2 with specs of:
Driver Units Mid/Woofer: 2 - 6.5" Diameter, Dynamic Balance Bi-laminate composite cone drivers, magnetically shielded

Tweeter: 1 - 1" Diameter, Dynamic Balance Silk/polymer composite dome, magnetically shielded
Power Rating 20 - 175 w/channel
Frequency Response 55Hz - 25kHz
Nominal Impedance 8 ohms
Sensitivity 90 dB

My questions are:

1. Are my Sony 3 way speakers better than the Polk 2 way speakers?

2. If the Polk speakers are better, is it a significant difference?

3. Do I have a better choice for towers (not bookshelf speakers) and a center channel than the Polks in the same price range ($400 - $500) ?

I do like the boominess of the Klipsch subwoofer. Thank you for your time and thoughts.