My thanks to everyone who has given me advice. I still haven't purchased one yet, but am getting very close.
I was going to go with the Dell, until I started getting feedback from all of you. My present computer was "built" and I was able to up-grade it over the years to its present state. So if I want the new one to do the same, I think I will get it built, as well. And thanks to all of you, I think I now know what components to get.
Now I just have to find someone to build it for me....
"Not everything that counts can be counted, and not everything that can be counted counts." (Sign hanging in Einstein's office at Princeton)