Perhaps an attack can get lauched in something like this?
I'm not spending a lot of time, but maybe this is along the right lines.
Over 2 dozen database games and none with the best move
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8...cxd4?? 9. Bf4 Qd7 10. Nxc7+ Kd8 11. Nxa8 Bb4+ 12. Bd2 and Black has nothing approaching an attack that White needs to be concerned about whatsoever. If Black trades bishops he's just helping White cement his material superiority. If he retreats his bishop with 12...Bc5 for instance, then White has 13. Ba5+ with improved chances of extricating his knight from the corner.
After the bishop trade I'm not certain white can save the knight. One must have a careful analysis before playing such a risky move as Nd5, as if the knight on a8 is lost he has no material superiority, but rather a material deficiency.
Material, schmaterial: Black's king is stuck in the center. After 8...cxd4?? 9. Bf4 my 2900/3000+ rated engine on two-year old hardware with dual processors, has White at least at +3.25. The only really tricky line I posted was 8...Qd8 9. Qh5!? (9. Bf4 is less risky) 9...cxd4 10. Qxe5+ and then 10...Kd7 11. Qxd4 and White has made a real sacrifice of it, but again Black's king is stuck in the center. If Black wants to survive he must play 11...Bd6 but after 12. c4 White threatens c5, Qxg7 (enabling Qxf7) and/or 0-0 (enabling activation of his Rf1).
9. ..Qg6 10. Nxc7+ Ke8 11. Nxa8 Qxe4+ 12. Qe2 Qxf4 and black gets 2 minor pieces for the rook.
I appreciate your guys' attempts but rest assured, Black is dead lost after 8...cxd4?? 9. Bf4 -- after 9...Qg6 10. Nxc7+ Kd8?? White does not need to rush Nxa8 but rather has the zwischenscach 11. Qxd4+, for instance 11...Bd7 12. 0-0-0. The other lines (8...Qd7 or 8...Qd8) are the critical ones, I am preparing to post to chesspub.com where GM Kosten was the last to post in their Spanish forum.
tyrannymutation is right about how much of an advantage white (totally winning) has, even though the lines are a little complicated for humans.
I've also come across a novelty sacrifice that gives white +3 in the Sicilian, but almost no one has played it in the database I looked at.
Oh and shepi13, I'm pretty sure Qxd4 is better than Nxa8 in the line you showed...
There are over 2 dozen games in chessbase with the following position/variation, two-thirds of them where White is rated over 2200 (and half of the rest where White is rated over 2000), and White did not play what seems to be the best move in any of them.