I have taken several whitetails with the 200 Hornady over 55.5 grains of 3031, including one at a hair less than 300 yards. The Whelen's effectivieness on game has been consistenetly excellent, well beyond what the paper statistics might suggest.
A great asset of the caliber is due to the modest velocity, there is no need for premium bullets. I now have taken 2 moose with plain old 250 grain Hornadys over 4064 .
RL15 and Varget are also great powders in the Whelen, and I would be inclined to start with them. Neither was available when I started loading for the Whelen. Check Alliant's and Hodgden's wesites for load data.
I think you bought a fine rifle in a great hunting caliber. The 7600 is tougher than many people might think. I doubt that either will ever disappoint you. Good luck.