Advice needed for new quality Speakers

[Exotic]

Hi guys, I am wanting to change the speakers in my Z but needed some advice. Shall I just upgrade the front speakers only and leave (or even disconnect, although can't I just use the fade function to put just the front speakers) the rears? I do have a sub as per my signature but may actually get rid of the sub in a bid to reduce weight and space, and just go with some high quality front spearkers, anyone done this before. I do listen to a few DVDs so will it be good to leave the rears in there for surround type of effects for DVDs movies etc?

 

My shortlist is:

Pioneer TS-E170Ci - 17cm Separate 2-Way Speaker System (260W)

•Maximum output power 260 Watt

•Nominal output power 60 Watt

•Impedance 4O

•Frequency response 30 - 33,0000 Hz

•Sensitivity (1W/1m) 88 dB

•Woofer size (cm) 17 cm

•Tweeter size (mm) 28,0 mm

•Network LPF/HPF:-12/-12dB

•Magnets Neodymium magnet

£100

 

Pioneer TS-A171Ci - Accelerate Series 6.5 inch, 17cm Component Car Speakers 350W

•6.5" (17cm) Component Speakers

•Maximum input power 350 W

•Nominal input power 50 W

•Impedance 4 Ohms

•Frequency response 29 - 29,000 Hz

•Sensitivity (1W/1m) 90 dB

•Woofer size 16 cm

•Woofer material Carbon Graphite IMPP Interlaced Aramid Fiber Cone

•Tweeter size (mm) 20,0 mm

•Cut-out Hole 128 mm

•Mounting Depth 54,3 mm

£90

 

Focal Polyglass 165VB 16.5cm Component Car Speakers 140W

•2-way 6.5" component speakers

•Polyglass woofer with butyl rubber surround

•TNB Aluminum/Magnesium inverted dome tweeter

•Non-resonant ABS/glass fibre basket

•Outboard crossover with 3-level tweeter control (-3, 0, +3 dB)

•Grilles included

•70 watts RMS power

•140 watts peak

•Frequency response: 60-28,000 Hz

•Sensitivity: 93 dB

•Mounting depth: 65mm (2-9/16")

£128

 

Noticed that the Pioneers frequency response seem much lower than it's rivals, any views on how good they are?