High amount of bitcoins buy sell is possible on some exchanges like local bitcoins, bittrex and poloniex. on localbitcoin.com u can find new sellers who are selling bitcoins in high amount and u can check their reviews from customers who bought bitcoins in past then u can make a deal but one thing is on localbitcoin u need to verify Ur account first then u can trade.
Judging from reviews, exchanges that listed by you are quite good. Actually, I’ve even used several of ‘em. But I’d also add
cex to this list. According to
CoinMarketCap, its volume is quite high. Sure, there are bigger exchanges, but this one is most definitely worth of attention, as it contains great amount of BTC and ETH.