you won't be able to run crysis on very high.. build your own and save money.
Go with a q6600 G0 and overclock it, you'll get better results than with a QX6700... even if it wasn't overclocked
get two 8800 GTs(good luck finding them) and SLI them so you can save money and still have good performance.
whatever you do, don't shell out the extra $300 for a q6700, definately not worth it.