Few days ago you would have needed only 80M to perform a 51% attack, if someone had really been interested to knock down the network he could do that by temporarily ordering a few number of virtual machines. It would probably have costed less than 1000$. Even that was too much to perform an attack, noone cares.

The Hashrate hasn´t been that low since December 2013, still in December the situation was better because it wasn´t that centralized - even though it was really bad:

As you can read from this post the Hashrate of Coinmine in December 2013 was about 90%. Today it has 98.96% with 406M Hashrate (don´t believe it? click here). There is basically noone solo mining. Quark IS coinmine.pl.

Waiting for Digitalindustry or Hillux to come and claim that Quark is the best and most decentralized currency.

I´d be interested in an explanation how Quark could ever get away from being centralized at coinmine.pl