Stick one of these in your Q6600 mobo, clock it to 3.6Ghz and get very good performance out of your existing kit. It’s what I do, and it works very well on my Asus P5K mobo of 10 years of age.
or this one in the UK
I run this with 8GB DDR2 RAM, triple SSD drives, and 4 monitors connected to an nVidia GTX 780Ti, and it all works beautifully, and I use some big VST’s
The Q9650 will give you around i5 performance when clocked. Many later CPU’s are not so much faster than this chip, they just use less electric. The Q9650 was an expensive processor in it’s day.
Yes a clocked i5/i7 will be faster, but will also cost you a lot more and won’t be magnitudes better.
So this is a good route if you are on a tight budget.
Compare this unclocked:
At 3.6Ghz the Q9650 is producing around 5000 on that scale.
Then compare that 5000 with the i5 numbers here.
Just be very aware that there is a huge difference between i5 and i7 performance across the range, and you could buy one which is not actually any faster than a Q9650, yet you will have spent a fortune as you will need a new mobo and ram to go with your i5/i7 CPU.
People have bought these later chips and been very disappointed with them and still not got good Cubase performance if they don’t choose carefully. Some of them are targetted at electrical efficiency, rather than computing power.
And to answer your opening question, yes definitely stick with a quality mobo manufacturer such as ASUS or Gigabyte. The tend to work better and be better supported as the years go by on later OS’s etc.