I used to think the same, WG, until this cycle. I had screwed up using letrozole before and completely killed my sex drive (I could get hard, I just couldn't get excited about anything) and had elevated liver values post cycle (probably partly due to orals, as well, however).
My current cycle, however, I am using letrozole at .625mg EOD and experiencing near perfect results from it, a lot better than my past experience with arimidex. For some reason, the letrozole, now that I have found my sweet spot, seems to keep my estrogen levels much more stabilized. Even though I agree that arimidex is a good compound, I always seem to fall in and out of the aformentioned "sweet spot," and find myself adjusting my dosage all cycle. From the moment I reached what I felt was just right with my current dosage of letro, I have not had to change a single thing.
As for the OP. You are 250lb, that's bigger than most of the guys on this website. If your body fat % is what you say it is then you obviously have a handle on what you are doing and I will not criticize your choice of compounds or amount used (though I would not have recommended them to begin with, and I'll just bet that your actual BF% is higher than 18%).
If you really want to keep the weight going up, I would think about adding equipoise, which should ramp your appetite up through the roof, and help you to meet your caloric goals, which is where, honestly, most of your gains are going to come from beyond this point. The gear will help most of it become muscle, instead of fat.