CPU and Motherboard update.

I have been using Sonar for some time now.  Started with Sonar 6 and been working with X1 Producer since it came out.
The computer I built is over 6 years old now, and it's time to update my hardware.  I am using an AMD Athlon Duel core 4200+
2.2 Ghz. with 4 gig of ram.  I also have a graphics card installed too.  My computer runs X1 with with little trouble until I get a project with a lot of tracks with soft synths and plug ins.  Time to update.  I get some freezes and pops when that happens.  

I am open to suggestions about processors and motherboards.  
I have another question.  Should I get a motherboard with onboard graphics.  I you have onboard graphics and a graphics card,
do you have there total memory combined?  Or does the graphics card bypass the onboard graphics memory?

I want to stick with AMD and I'm fond of Asus motherboards..

Any suggestions would help.

Hardy

I am open to suggestions about processors and motherboards.

I have another question. Should I get a motherboard with onboard graphics. I you have onboard graphics and a graphics card, do you have there total memory combined? Or does the graphics card bypass the onboard graphics memory?

I run an i7 2600k chip and use the graphics on that.  I do have an Asus board but I think I've been lucky so far.

I was staunchly AMD before but being able to get a sub £500 machine built that performs seriously well for all that I use it for, (including Sonar) plenty of grunt and good low latency, I'm very happy just now.