Difference in B&W sound

More open could mean many things. It would be a better comparison if you were to listen to both speakers without any processing. That way, you are hearing more of what the speakers can so.

The Matrix series, as well as all 800 series since 1974, use the Kevlar mid.

Speculating here, but having owned both Matrix 802s, 804s and Diamond 804s, to include both at the same time (804s), this may be very simply a matter of synergy with your electronics. As a rule B&Ws need power to open up, and (this is the speculating part, as opinion doesn't count on science) I think the newer models may even be more power dependent. If it were possible, I would do the same listening test with a very good high powered amplifier and see what happens. I suspect the N804s would surprise you with the sound quality. Also, the matrix series sound great - just because they are older doesn't mean they are bad. In the right room with the right electronics and music they still produce nice music, which some might prefer. The newer models might have tighter bass or better treble, but in the end these things can be a matter of preference and system synergy.

The Parasound 2003 is a high current amp = Continuous Power Output
> 200 watts RMS x 3, 20 Hz - 20 kHz, 8 W, all channels driven
> 300 watts RMS x 3, 20 Hz - 20 kHz, 4 W, all channels driven
Current Capacity
60 amperes peak, per channel
Slew Rate
> 130 V/μsecond
Frequency Response
20 Hz - 20 kHz, +/- 0 dB
Power Bandwidth
2 Hz - 150 kHz
Total Harmonic Distortion
< 0.05% at full power
< 0.006% typical levels
IM Distortion
< 0.03%
TIM
Unmeasureable
Dynamic Headroom
> 2 dB
Interchannel Crosstalk
> 88 dB at 1 kHz
> 74 dB at 20 kHz
Input Impedance
50 kW per channel
Input Sensitivity
1 V for 28.28 V Output, THX Reference Level; 1.5 V for full output
S/N Ratio
> 98 dB, input shorted, IHF A-weighted
Damping Factor
> 800 at 20 Hz

The 5250 = Continuous RMS Power Output
20 Hz – 20 kHz, Five Channels Driven
250 watts x 5, 8 Ω
385 watts x 5, 4 Ω
Current Capacity
45 amps peak per channel
Frequency Response
20 Hz – 50 kHz, +0/-3 dB, 1 watt
Dynamic Headroom
1.6 dB
Total Harmonic Distortion
0.025% at full rated output
0.02% at average listening levels
IM Distortion
0.05 %
Transient IM Distortion
Not measurable
S/N Ratio
114 dB at rated output, IHF A-weighted
106 dB at rated output, unweighted
93 dB at 2.828 V output, IHF A-weighted
84 dB at 2.828 V output, unweighted
Input Impedance
33 k Ω
Input Sensitivity
1 V in for 28.28 V out, THX standard
1.6 V for full rated output
Inter-Channel Crosstalk
85 dB, 1 kHz
73 dB, 10 kHz
67 dB, 20 kHz
Damping Factor
Over 150 at 20 Hz

"01-17-15: Jimmy2615
Speculating here, but having owned both Matrix 802s, 804s and Diamond 804s, to include both at the same time (804s), this may be very simply a matter of synergy with your electronics."

He's right. The 804's may be revealing more details than the 803's, and are just bringing out the flaws in the other components. I would demo a different amp, if you can. The Parasound you have is OK, but you can do a lot better.

Since you already have the equipment, here's something else you can try. Take your Parasound 5250v2 and use 4 channels to power the speakers instead of 2. Sometimes it makes a nice diffrence, but not always. You just have to try it. Make sure you remove the jumpers from the binding posts on the speakers, if you're using them.