I'm over one per acre.But it has to due with what fits you. Two Steigers. Less than 40K between them. Less money together than 9x30 or 7140 that could do the job. One breaks. I just grab the other. 2+2 on fertilizer buggy. Twice what I need. It was paid and here. Perfect job for it. 7140 on planter. Was the best deal for my fit. That doesn't count the tractor dedicated to the sprayer, or the 2  06 model sitting around. One of which picked up the slack when the 3788 dumped a clutch. Down time 1 hour. Tractor was fixed in July. So I don't worry about hp per acre. I look at what is dependable for me. And how can I keep things rolling without breaking The Bank of Don.