IMO, replacing the orifice is the better way to experiment with higher btus. The Q2000 gas valve assembly might cause your grill to be too hot. Going the spare orifice method, you can choose precisely how many BTUs you want. Eg. For 10000 BTUs, get an orifice with a 0.038" hole.
I believe someone on this forum was bumped their Q1200 to 10000 btu using a 0.038 orifice and claimed it worked well.