Judging by your signature you could definitely use an upgrade at defense. Any one of those three guys could be good.
As for comparing forwards with defense, I generally use the rule of thumb that a 70 point forward is roughly equivalent to a 35 point D Man. Last year there were about the same rarity.
I think Pavelski could have 80 point upside, and any one of these three blueliners could have 50 point upside. That means these players have roughly equivalent value. It would be fair to ask for one of these defensemen for Pavelski, though it will of course depend on the needs of the GM you want to trade with.
NOTE: I especially like Gilbert. He has been playing extremely well, even with both Souray and Visnovsky in the line-up, and stands to be a future PP quarterback on an offense-first Oilers squad. It\'s a toss up between Niskanen and Yandle, but I do like them both.