I highly suggest substituting the Asus A7V8X-X with the Asus A7N8X-X board. The A7N8X-X is significantly faster, more upgradable, and more stable than the A7V8X-X. It should cost no more than $20 more.
The differences are that the A7N8X-X uses the nVidia nForce 2 chipset and can accept 400 MHz FSB CPUs as an upgrade (the 3000+ and 3200+). The A7V8X-X uses the VIA KT400 chipset, which does not support a 400 MHz FSB (but does support DDR400 memory). It is less stable IMO as well.
Other than that, I think a 300W supply is a bit small. If upgrading this is not feasible (comes with the case) keep in mind you may need a bigger power supply in the near future. (A 330W Antec Truepower or 350/360W Enlight or larger would be good enough.)
Also, if you are using PC2700 memory, consider pricing the 2400+ and 2500+ CPUs. The 2500+ is by far the best bang for the buck right now. It should be no more than $25 more than the 2200+. The 2400+ might only be $10 more than the 2200+ as well. I wouldn't suggest the 2600+, as for gaming the 2500+ is just as fast and costs at least $20 less.
512 MB of RAM is plenty. 1 GB is really a waste unless you plan on doing some serious video editting in the near future. Your money would be spent better on other items (like going to the 2500+ CPU, larger power supply, bigger hard drive).
Also, price out the difference in price between the 40 GB drive and an 80 GB drive. It shouldn't be more than $20.
Whatever you do, I *strongly* recommend substituting the A7N8X-X for the A7V8X-X. It is a far superior board.
As for the price, that seems fine. Current resale in my area adds up to $690 for the closest items I can find to those.