My guess is that the 6.1 will stay at 425 hp for 2008, with a 500+ hp 6.4 or 6.5 in 2010. (I hope that I am wrong because I intend to buy a 2009 SRT).

You have to remember, however, that the additional cost of the SRT is not only due to the engine but the suspension, brakes, tires, trim, etc.