Guys, for soundproofing,
my personal experience on my previous car was,
rubber seal on door frame + bitumen material (i guess tis is d dampening pad that u all mentioned) + superlon material (insufflex) did really handle their job well,
what i can say is miss one of them will affect the effect,
all of them have different uses and effects..
For me bitumen is to BLOCK all the road noise and other noises such as metal rattling noise, so called "mid-bass echo",
while superlon is to ABSORB the rattling noise produced by plastic panel, and it also can absorb some of the noise produced by plastic + metal contact too..
For me they hv different uses

Another important thing is WIND NOISE, this one will very obvious if u drive above 100km/h (especially for my previous car which is a KENARI), what i did last time is change all the rubber seal on door frame to the one with at "D sealant",
and i squeeze some superlon inside the front fender there (there's a big hole in the fender if u see from dashboard/front door, this place can bring alot of wind noise into cabin). For my kenari after i squeezed the thing to cover the hole, the wind noise was reduced 40% at least

Ohya forgot to mention what I did on my previous car was,
Full car bitumen soundproof which covered:
Front door dual layer, rear door one layer, rear bonnet dual layer (Kenari's rear bonnet is a door actually), plus floor whole covered including spare tyres area, and firewall area too!! Oops i did some on my A-pillar too
While superlon I did it for my rear door panel, some floor area, firewall area, roof top, A pillar plus B pillar.

Added on October 8, 2011, 2:13 pmFor our Saga (or at least my FLX),
I noticed the main noise for nw is the road noise (which is killing me), and also the engine noise...
But i don't dare to take out this car's dashboard to do soundproofing la =.="
To kill road noise i guess have to do soundproofing for floor area and most important part which is tyres area dy, but I'm afraid that using bitumen material my FLX wiil heavier alot

Added on October 8, 2011, 2:17 pmChecked dy, I think is misalignment issue
Yea, going to ask them adjust for me the next visit to SC

I did all that you did for ur Kenari on my BLM, except firewall now, becos this one can't DIY myself. Furthermore for door is quite overkill, Front door 4 layers + rear door 3 layers.
My gf own a Kenari as well, if direct compare without SP, Saga road noise tends toward midbass frequency region, which might kill ICE and long journey comfortable, and this midbass noise also very hard to kill by SP only, dampening is a must if you talking about serious SP. While Kenari is tends to high frequency range, which can covered by soundproof more than dampening.
For FLX, if you want, do a proper dampening and SP like ur previous Kenari, it will help to reduce road noise and engine noise alot, yes, only 4 doors the outcome is impressed already.
Finally, yes, the car will become heavier, my rear suspension is almost 1cm lower after done all the dampening and SP + 1 large sub at boot, FC wise, the effect is negligible, but the comfortable outcome is just unbeatable.