If you're looking to transport 6 bottles of booze, I'd get an airline shipper case. It's a cardboard box with inserts to secure the bottles. I've used them many times with wine and whisk(e)y. Sometimes wineries/distilleries will give you one for free if you're buying a bunch of their stuff, or I've bought them for $15-20 at shipping stores. Airlines are used to seeing them and know how to label and handle them.

I once had an airline tell me not to pack more than one bottle of wine per checked bag, but it sounded like their own rule - not an FAA or customs rule. Basically, "we don't want red wine all over everything." You can also buy travel sleeves for individual bottles for a couple bucks apiece.

I have also shoved 2 bottles of whisky into a single checked bag while clearing customs at a US airport and rechecking it with the airline. Not sure if the airline would have been happy to see me do this, but the bags made it home in one piece. I've never done this when there was already booze in the checked bag.

No idea how different countries tax booze when you're declaring excess over the duty free allowance.