You will probably be happy with the performance of that machine on SketchUp and other CAD projects with the specs you have identified. I have been pleased with my Dell Precision experience. I have bought 5 Precisions for my company and for personal use over the years. I was running SU v.4 when I first purchased a Precision and each of them has been a workhorse.
There might be a reliability benefit, I am not sure if big enough to justify the cost.
But my opinion about the Quadro cards is that if you decide to have one, take one of the expensive models. The K620 is rather entry-level, meant primarily for 2D CAD, and you would get much better performance by getting a Geforce of about the same price.