Theres not many motherboards left on the market to support that processor , as an owner of the same motherboard as you I'm afraid it was one of the fastest on the market at the time.
My suggestion is to change your current ram to something faster than 1333mhz at least 1600mhz will lower timings to notice a difference
With the right memory choice and experience the Striker II extreme overclocks ram very well.
You should also consider overclocking your Q9650, you will notice a huge difference from the standard clock of 3ghz.
I'm running mine at 3.8ghz as I found it to be stable with BF3.
If I dont run BF3 I can overclock mine to 4Ghz stable.
This would be a better option than looking for another motherboard to replace the Striker II extreme, as I don't believe there are any motherboards available with that chipset that support 16gbs of ram anymore.
Adding an SSD can also give you a good performance boost to an ageing system.