I am going to have to say no, that isn't good enough.
That is a 400W continuous power supply...only 450W peak, which means it can't sustain 450W for long.
Only 324W available for 12V. It has a dual 12V OCP design too with 14A and 13A. Usually with those dual 12v designs the CPU connector is on one output and everything else is on the other output. My guess is the CPU is the 13A(156W) and everything else is on the 14A(168W) output. That means you are going to have to try to run your SATA drives, your fans and the videocard from 168W. The HD4870 can use 130W all by itself.
I'd say it might work, but you will certainly be bumping your head. You would be much better off going and getting a more capable PSU.