Wire each individual sub in parallel so that each sub is wired to 2ohm. Wire each pair of subs in series to get 4 ohm. Wire the two pairs in series to get 8 ohm.
for 2 ohm:
Wire each individual sub in parallel so that each sub is wired to 2ohm. Wire each pair of subs in parallel to get 1 ohm. Wire the two pairs in series to get 2 ohm.
for .5ohm:
Wire each individual sub in parallel so that each sub is wired to 2ohm. Wire each pair of subs in parallel to get 1 ohm. Wire the two pairs in parallel to get .5 ohm.