Basify and extract the MDMA base with DCM. Repeat al/hg a/b washes many times and collect all MDMA base in DCM.
Then distill off the DCM and vacuum distill the MDMA base. The increase in quality of the end product is well worth the effort.
Then crystallise by your method of choice. I used to simply dissolve the distilled freebase in acetone and gas in that, works very well, but its up to you.