Well I am in the same situation as you.
I never had an Antminer but I want to buy one.
I am in EU, and can pay only with visa card, or try to buy bitcoins with card to pay.
So I was looking on alibaba site for at least one month, but like you I don't know who to trust.

There are sellers with videos, and have their company name written on a paper.
I will try to post links here, hope I don't break any kind of rule.
This should provide proof that they are legit, but again, maybe there is at least one person in this world who bought one from alibaba and happens to have an account here and can help us out!
All of them have Transaction numbers (6 months) and 1/4/6 years registered on alibaba.

1) https://www.alibaba.com/product-detail/Bitmain-Antminer-S9-14TH-s-Bitcoin_60696358306.html?spm=a2700.7724838.2017115.1.8415ad9CDeRNw
2) https://www.alibaba.com/product-detail/hot-sale-fast-delivery-antminer-bitcoin_60707529187.html?spm=a2700.7724838.2017115.24.8415ad9CDeRNw
3) https://www.alibaba.com/product-detail/Antminer-S9-13-5TH-s-098W_60720051284.html?spm=a2700.7724838.2017115.34.8415ad9CDeRNw
4) https://www.alibaba.com/product-detail/Quicky-delivery-for-bitmain-antminer-S9_60701909360.html?spm=a2700.7724838.2017115.303.8415ad9CDeRNw

One information I can provide is that they asked me what TH do I want? 13.5 or 14? and when do I want it because the price differs. Like if I want it in 1 week is 5000 USD, 1 month 4000-3000 USD and so one.

It would be extremely helpful if someone who bought from them can come with a feedback to help out people who have only credit card.

Cheers!