Anything but S7 is a waste of time. Especially having in mind expected mining diff increase. If I were your, I do go PoS or build a rig cause SHA 256 mining for home users is the thing of the past. Unless you are a whale.
Definitely not a whale. 
What's PoS? And building a right, you mean, use GPU mining?pos is for altcoin, does not belong here, it's proof of stake
anyway it's not true that only the s7 has a reason, s5 is good if you don't mind electricity, because it cost much less and the roi is faster
s5 deliver 1/4.2 of the hash, while costing 1/6-7
This community is super awesome! Thanks for chiming in with some excellent advice!
for an s7? where at that price, because if that is true, it would be amazing, very cheap indeed
i would grab it without thinking, roi is in 2 months with that investment
Amazon prices are usually higher than the prices you pay on this forum. Same goes for ebay... I've found some good deals on alixpress, but you have to be carefull with them to...