"Psych Up copies both the positive and negative changes to the target's stats and replicates them onto the user. The target's Attack, Defense, Special Attack, Special Defense, Speed, accuracy and evasion are copied. Any changes made to the target's stats after Psych Up is used will not affect the user's stats."
From Bulbapedia, the wording seems to suggest it ignores any changes to yourself, so you'd end up with +2 SA in your example, but I've never tested it so who knows.