I recommend Abt appliances as a very reputable website. However, you are too early to be ordering your appliances if you are just in rough-in of your new construction. I.e. you don't even have your walls, floors, ceilings, you don't have your plumbing or electrical yet. Keep in mind that the clock starts ticking on the appliance warranty upon delivery, not upon installation. You would be foregoing valuable warranty time by ordering now. And why should you? The manufacturers build the cost of warrantying the appliances into the price, so you are paying for warranty that you are foregoing by ordering this far ahead of installation.

Furthermore, if you order now, where are you going to store the hood and cooktop? New construction sites are notorious for things getting turned over, or crushed, or stuff piling on top, getting wet, or even, getting stolen.

Also, it often happens that people change their minds about which appliances they want as their kitchen plans gel. You may find that you'd have preferred a rangetop instead of a cooktop, for example, or a switch to induction, or a different hood than what you are thinking of now, or all sorts of things that might make you change your mind at this stage.

P.S. since you are in new construction, make sure they install a good-sized kitchen exhaust duct. It should be 8" or 10" in diameter. Don't let the GC tell you that "6" diameter duct is fine".