We are just now getting our 06's and we ordered them 3 months ago. 8 weeks is unrealistic for a car that they have to ship from Australlia.
I'd make your decision on two things.
1. How are you going to pay for it? Lease, finance, cash. 06 will lease the best, 05's will finance the best, and 04 will be the cheapest to pay cash for.
2. How long are you planning on owning the car? If for a year or two then lease an 06 and roll on. If for 3 to 5 years then I'd say get the one that you want the most. Like Mike said, if a faster seat is important then get an o6. If it is not important then roll an 05.If you are keeping the car for more than 54 years(really keeping it for that long) then get the car that you want. It really does not matter what rate or what price. I know guys that financed their cars for 84 months because they are keeping theirs until the wheels fall off or if the value goes through the roof, which is possible.