Well let's start with telling us what you currently have, followed by what you feel could use improvement. Telling us you have a 20k budget will get you very wicked system (CPU A.K.A. processor, motherboard, RAM).
Also this usually goes without saying, but seeing as how you labeld what you thought a CPU was... When replacing CPU &/or motherboard, it is best to reformat (completely erase) the hard drive (which stores all of your architectural rendering data).
If you don't already have an IT dept to turn to (which stands to reason, hence you asking here), take your current system to someone or someplace that can perform a back up for you to retrieve after the upgrade.