If you're trying to get a good power supply at a low price, the Antec Earthwatts 650W PSU is available for $60. But if you must have a modular PSU, either get the HX520 somewhere else for less, or find a different model, like the Silverstone ST70F.
For a hard drive (in the future), consider either the Western Digital AAKS or the Seagate 7200.11 320GB or 640GB hard drives. They use 320GB drive platters that makes them faster than earlier models.
The P45 chipset, in addition to its dual x8 CrossFire support, supports PCI Express 2.0. However, today's PCI-E 2.0 cards are backwards compatible with the PCI-E 1.1 slot on P35 motherboards.
With the prices of P45 motherboards being similar to the P35 boards, however, there's no reason why you have to choose one over the other.