my idea of stacking starts from highest gain to lowest gain. Pedal with highest gain gives the overall tone, pedal with the lowest gain gives the over all volume.
e.g. (my setup) Big muff > Super Blues pro > Soul food > amp
depende sa hinahanap mong tunog brother. I do it both ways, depending on the need.
I used to have a setup like this:
Guitar > British Distortion > Transparent OD > Amp
nico is right. the flavor come from the first dirt in the chain, and then the lower gain dirt will give the over all volume/eq shaping options.
now, I have mine setup like this:
guitar > TS9 > DLS MKiii > Amp
reason being the TS9 just pushes that DLS to sweet ecstacy. might be because the DLS is a preamp and the TS9 is supposed to be at its best in front of an amp.
in your case, try all options! and find the best sound per your taste!
I'd do it this way though.
SD1 > BD2 > SL Drive. the SL Drive is a Marshall in box hence I believe itll be best if its the last one in the dirt chain. unless you want to increase volume after the SL.