For the majority (95%) of us, it is not desireable psychologically to "blow up" 40 lbs. on a first cycle or to be introduced to anabolic steroids with a very harsh regimen which may actually have a surprisingly big impact on your body image, interactions with others, etc. And 40 fast lbs. may evaporate fast, causing more psychological confusion.
Just look at that really big juiced up looking guy at your gym, the one who is maybe not naturally a big guy but now is at 5'9" 240 or something. Now ask yourself if you're really sure you want to be that guy. Take a gram on your first cycle, and you'll be getting closer to that guy than maybe you realized, and maybe closer than you wanted if you were being honest about it. The people around you will react to the difference. It is far easier to shrug off / explain 20 lbs. than 40.
So, if in doubt, go with less and take care of your diet, training, and rest.
The other side of it is, you just might not be ready to train hard enough and eat enough calories to justify 750 mg. a week of sus. So it could be wasted gear and the same gains could be achieved on 250 mg sus stacked with something like deca or dbol (or both).
Why not try 250 mg/ wk sus, 200-300 mg/wk EQ, and 25 mg of dbol a day for only the first 4 wks.? You should get 15 permanent pounds off that.
If you should decide later you want to be huger, nothing is stopping you from going on another cycle and upping the dosages then when your body is more accustomed to the weight.