Brett,
16GB is plenty and easy to upgrade.
-SSD is a must these days. It’s the #1 speed improvement you’ll get on a computer. SSD prices are also cheap enough to get a 256 gig drive and use it for your working files as well. Will help considerably when saving big files. You can always move them to an archive folder on the HDD when needed.
-For rendering, cores over clock. For day to day usage, it’s the opposite - fastest clock speed since all those other tools are only single threaded for most tasks . If renderings is a major time sink and huge part of your workflow, opt for as many cores as you can afford. If rendering is an occasional thing and most of your renderings finish in a few minutes (like most Keyshot renderings will on a quad core I7) then optimize for a 4770k and save the money.
If you are happy with your current GTX setup then don’t worry about upgrading to a Quadro. But the 200 series cards are pretty dated, so an upgrade to something like the 760 (or even an older 660) would help.