Does this mean a system a bit over 1.5 million dollars could take over the network and make a load of false bitcoins?
No, it does not mean that. The most profitable attack that anyone could perform on the bitcoin network if they controlled more hashing power than the entire remainder of the network would be to reclaim coins that they recently owned and spent. They could not take coins that they never owned, not even from the most recent block. Nor could they make bitcoins beyond the parameters of the system, legitimately or not.
And this attack, as difficult as it is, only lets the attacker respend his most recently spent coins because it allows an attacker to rewrite the most recent block. However, the difficulty for the attacker goes up dramaticly the farther back in the blockchain the transactions that he wishes to overwrite might reside. Otherwise the honest network will continue to outpace his total-proof-of-work, based upon how far back he must go to get at said transactions.
