If you wanna chug a lot, get a high gain amp.
Single coils are good for funk and blues rock - mainly cause the quack and twang of single coils are suited for these two styles. Also note definition when playing funk chords are easily heard on single coils. It also depends on what kind of pickups (magnets/windings) are used. For these two, mid/low-mid output is suitable.
High output single coils would gravitate you more towards the basic rock/hard rock tones.
humbuckers are good for hardcore, basic rock, its not too good for funk because it may get muddy and note definition is not as clear when playing 3 note/4 note chords. It also lacks twang and quack, but the output is smoother and thus used for classic rock/rock/hard rock.
BUT, of course it is not limited to these two, you can always use humbucker equipped guitars to play funk and blues rock. Its just a matter of preference.
Answering your question as to stacked humbuckers, you might wanna try looking at seymour duncan's line of single coil sized humbuckers. They are a direct retrofit into the cavity of the mex strat.
Just to let you know, Tom morello of Audioslave/RATM uses a strat that has been modified ( re routed for FR and locking nut + hot rails in the bridge )
You might wanna do some research on the hot rails to put into the bridge for your lead tones.
And leave the single coils in the neck and mid for rhytmn.