Easily, even if you are overclocking.
One of my systems has a Q9550 overclocked to 3.6 GHz, 4 GB RAM, a GTX26s, a Gigabyte EP45-UD3P motherboard, 3 hard drives and an optical, and a Soundblaster card all powered by a Corsair 750TX.
Running 3 instances of Prime95 to load the CPU and 3DMark06 to load the GPU, it pulls 375 watts from the wall as measured by my Kill-a-Watt meter. Figuring 80% efficiency, the system pulls 300 watts from the PSU.
That is about 60% of the rated capacity for your PSU.