Overall, I would just try to get on group buys with trusted people here through escrow.
Or just buy directly from bitmain or manufacturer website.
Firstly because resellers charge a premium, making it much harder to ROI.
There is basically no power left in your hands after you send your BTC to them, manufacturer like bitmain you can trust but not all these companies may be as reliable. As you have basically no power over them after you send them your BTC, there is no buyer protection.
So if they accept paypal, that might be a safer option.
Eastshore is safe to send your BTC to,
Heaven tech is rather unorganised and has a high premium, I had to prod the guy 2~3 times before sending my L3+.
Segree/Bitwinkor I'd personally never buy from them again.