ἐννοήσατε δὲ κἀκεῖνο τίνα πρόφασιν ἔχοντες ἂν προσιοίμεθα κακίονες ἢ πρόσθεν γενέσθαι
Does this an belong to both exontes and prosioimetha?
It goes with the optative, necessarily, not with the participle. But its position shows that it is continuous with the participial phrase.