The Core i7s are looking to be fairly pricey. ~$300 for their lower end. Regardless, you should look at multi-core processors. There will be more software out there that will take advantage of it.
Depends on what you want to use RAID for. Do you wish to do RAID 0, 1, 10/0+1, 5, etc...? SLI is nice, but most with cards becoming better every quarter, it might better to wait for a better card.
If your system can run COD4, then you can afford to wait a little more.