No. Make sure to update your motherboard bios to the newest one available. Since you are going down in clockspeed do you run any programs that can take advantage of four cores? If not the Q9550 would actually perform slower unless you overclock it.
it dose not nessarly run any faster than Quad's just that the Games only uses 2 threads. But it is nice to have a Quad when somthing like your Anti-Virus starts to run a scan or any other backround task.