I wasn't completely sure about my concerns, so I wanted to do a little research before I addresses issues that might not be issues. Looking at the current EPDs of the first two sires, Lock N Load & Star Power, both bulls have the same weaknesses on paper: MCE, Milk, Marbling, and API. I do like Upgrade; I don't think there is one bull that is the best choice for every female out there. Particularly in regards to the below average MCE and the fact that she is a heifer, I would be looking more at a real calving ease bull for the first calf. I know you mentioned you would like a purebred, but iI wouldn't discount the Angus faction too much...SimAngus cattle are extremely popular, and there are probably more options that will improve the areas you might want to improve. If you have your heart set on a purebred calf, I would look at some bulls that compliment your heifer's pedigree, and I'd really pay attention to the calving ease, birth weight, and MCE EPDs. Take a look at Top Grade, for instance...he seems to be a really easy calving, light birth weight Upgrade son, and he's a 3/4 blood so your calf would still be a purebred.
I'm just throwing out some of what I would be thinking about if I was choosing a mating on this female. I would still think about her phenotype and your plans for the calf in addition to everything I've mentioned in regards to pedigree & EPDs.