One positive point not yet mentioned about the C. cyaneopubescens (Green Bottle Blue) is that they are nice to look at at every size. They don't start out brown like most of the rest, and they go through multiple color phases as they grow. I ordered one with the G. pulchra I just got. Here's a pic...
Lasiodora parahybana, Brazilian Salmon Pink Bird Eating Spider is a great choice if you already have a Golden knee. They are more skittish and not really handleable but get huge and are very active. Best of all they are really cheap and grow very fast. Spend around $30 for a 1 to 2 incher and it will be 5 to 6 inches a year later. A bit more challenging, they might bite if provoked but mostly will just fling hairs. No beauty contest winners though, big black spider.
For what I consider a beautiful spider you might also want to consider, P. irminia. It is arboreal and very fast, and aggressive. I just got my first one and I have never seen a more beautiful tarantula. It has an elegant look to it. It is lightening fast! When it strikes a cricket, the movement is so quick it is barely perceptible by the naked eye. Better yet order both!
With all the great feedback from all of you, I've decided on a C. cyaneopubescens. I know my local pet store has one in stock so I plan on talking to them about it and making arrangements. Thank you all very much, you've helped a ton!