The 440 isn't a very powerful card.http://www.hwcompare.com/8229/geforce-gt-440-1-5gb-vs-geforce-gtx-460-1gb/
I wouldn't recommend buying anything less than a GTX460 in the nVidia line as even that card is aged and pretty much phased out. Now that comparison isn't true life results or anything; but it does give you a good idea.
You're GPU is probably the weakest link paired with that X2. The best idea I have for you is to upgrade to a GTX550Ti or better card. I hope this helps as I don't believe overclocking that CPU is going to do any good for you.