Opel, the last one you tried to link to, the i7 for $649 is a pretty smoking deal for the specs. It's basically exactly like the i5 version but with a more powerful processor, all for the same money. I would say that if $649 is the target budget, that i7 will serve you well.
Strong processor, wicked fast 512GB hard drive (NvME), 12 GB RAM, better screen resolution than the i5.