Peggy,
Actually 3dANOVA4 may not make things any harder to explain. Because you are forced to use one of your factors as your 'Subjects' variable in order to make the ANOVA a repeated measures design (there is no -repeated option akin to the -paired option in 3dTtest), having 4 factors may not necessarily complicate things more than the 3dANOVA model. I agree that 3-way or 4-way interactions may be hard to interpret, but forcing your 3 factor, within subject experiment to be analyzed with a between subjects model due to software limitations is, I feel, more problematic.
Christine