(Wow Skepto, you've really declared open war on your new teacher, haven't you?

)
How about this for an idea: instead of Op.3
1 and Op.6
3, how about Op.3
3 and Op.6
1 - the Grande sonate and the Sonatine in A minor? Or just the Grande sonate? As long as we're talking about underplayed Alkan (yes, all Alkan is underplayed, but these are underplayed even by his standards), the three non-'Quasi-faust' movements of the Grande sonate all arguably fall under that category.
And as for pieces from Op.39, I must cast my obligatory vote for my favourite from that set, the also underplayed 'En rhythme molossique' in D minor, Op.39 No.2 (one of the four Op.39 etudes Hamelin has not yet recorded). The coda in which the piece scrambles to get the energy together to go out in a blaze of glory in the major only to expire with three muted chords in the minor is one of my favourite Alkan moments.