I'm now looking at updating my studio with new Thunderbolt audio interfaces and a new computer.
 
I've started doing mixes with 32 audio tracks and ran into digital crackling issues with my old computer system.  The crackling could be eliminated if I started removing the number of Sonitus Reverb plugins being used on individual audio tracks. When the crackling started I noticed the CPU was pegged but I still had headroom in memory.
 
My old system has 4 gig of memory and is a Dell Pentium E5700 Inspiron Dual Core CPU 3.50 GHZ, Windows 7 64-bit.  Therefore, I'm wondering what minimum CPU and memory requirements in my new system will be enough to prevent this issue from happening.  Is a standard video card (motherboard) enough or do I need a more powerful one as well?
 

FWIW, You'd get more efficient use of CPU by using several reverb plugins on Aux sends (instead of applying reverb to individual tracks).
 
Any modern build i5 or i7 (4GHz or faster)... that's well configured for DAW purposes (low/consistent DPC Latency) will easily handle mixing 32-track projects.
 
You may want to have a look at the other thread where we're discussing Thunderbolt.
Thunderbolt alone will not solve issues like high DPC Latency... or yield extra DSP processing power.
If you go with a Thunderbolt audio interface... make sure you know all the details.

Thanks for the "heads-up" on Thunderbolt - I'll have to read those other threads.  Good idea for using the Aux sends instead of individual tracks.  I'm looking at an i7 (4 GHZ) processor.

For an office or gaming PC you can buy off the self. For a DAW I believe you are further ahead to either build your own or buy from a builder like Jim. If you build your own you'll have more than double the quality for the same money. You buy from a DAW builder your arse is covered and you'll have top shelf service to set things up properly. 

Agree with Cactus... check out Jim's Studiocat website to see if he has something that fits within your budget, whatever that may be...