the E450 and the E550 are both better than the E408, E213.
In terms of how much better ? its hard to quantify as the E408 is no slouch, the E213 is no slouch either.
the E550 is purer, more detailed than the E450. the E550 is also more transparent but the e450 is more fuller sounding than the E550.
With your JM lab either the E550 or the E450 can drive them easily. Its just now a matter of preference.
Either way, you can't go wrong!
In terms of how much better ? its hard to quantify as the E408 is no slouch, the E213 is no slouch either.
the E550 is purer, more detailed than the E450. the E550 is also more transparent but the e450 is more fuller sounding than the E550.
With your JM lab either the E550 or the E450 can drive them easily. Its just now a matter of preference.
Either way, you can't go wrong!