Ide use a jaycar responce amp for the subs definatly, 2 x 150rms with bass turned up runs really well with 2 12inch subs, Ive got it running now in a car, Verry happy with responce amps and quality of sound,
Depending on how good the subs are, You could also use a jaycar 4 x 100rms amp, Once again i have this running in a car with 2 12inch subs, bridged, Bridging is no problem, Its basicly just putting the wires in a different slot in the amp giving u total of 2 x 300rms output from ur amp into ur subs,
Theres the subs solved for anywhere from $150 - $300 for either a 2nd hand jaycar amp or a brand new one for 299 i think if u chose that option,
did u mean 6 by 9's in ur parcel shelf? either way, you could get a small amp to run them, depending on ur rms of ur speakers, could get a small amp for like $30 - $100, I have a mate that has a small 2 channel amp at the moment... i think he wants like $30 for it..
Ide then put both amps onto 1 switch in the dash somwhere, Once again simple, a $3 switch from jaycar and u split you remote wire and hook onto the switch, This way u can cut ur subs instantly, If ya see a cop switch ya sub off etc etc,
Have the smaller speakers the 6inches and the 4 inches both running off the head unit, Front and back speakers, This way if u get sick of the doof doof u can have a nice surround front and back speaker system u can control/fade from the head unit, and flick ya switch ya can have ya good speakers cranked and a massive boost of doof doof
My personal choice, had similar in lots of my cars, havn a head ache flick the switch and got some nice cruisy treble happenen
Also 8 guage wire would be fine to power both ur amps, also get this from jaycar LoL, most of my cars have been sponsored by jaycar,
Oh and with the subs, Yea a monoblock, Once again from jaycar could be a good way to go

my 2 cents worth