There are various ways of dealing with the problem of the very large number of voxels in your statistical image.
For rigorous statistical thresholding, you will one of these options:
Random Field Theory - see PrinciplesRandomFields.
False discovery rate - see PrinciplesFalseDiscoveryRate
Permutation testing - see PrinciplesPermutationTesting
Bayesian correction - see the articles listed under http://www.fil.ion.ucl.ac.uk/spm/doc/biblio/Keyword/BAYESIAN.html
Sometimes you may want to use a more liberal threshold that does not allow strong control of false positives - for example to report 'suggestive' rather than 'significant' results.
A perfectly reasonable option is to use a reduced threshold, still correcting for multiple comparisons.
Another is to report your UnthresholdedEffectMaps.