I'd recommend filling this out and then we can assist you better: http://www.tomshardware.com/forum/261222-31-build-advice
But for architecture programs and even just Photoshop and Illustrator - you don't need a 2600K. It's mainly reserved for high end video and 3-D rendering apps that require hyper threading.
I work in an architecture / engineering firm and I'll tell you that most of the programs we use are so far behind the hardware that, let's put it this way - I'm the only sandy bridge build on the network. We use a lot of Autodesk products with custom plug ins, Adobe Acrobat, and a few CS4 programs with plug ins, and I'll tell you this. Anything Autodesk makes - including 3-D Revit and other similar programs are so far behind the hardware that even a 775 system will run everything pretty smoothly.
Even on full CPU loads - I use an i3-2100 (for now, I'll probably upgrade in the near future) with 16GB Corsair RAM and a Crucial SSD - I don't come anywhere close to using 80% of the CPU load.
If you fill out the form I can recommend you a good built that's pretty similar to what I use and it will handle everything you can throw at it.