Whiteflash and HPD for great upgrade policy. Better than bluenile. Just spend a dollar more versus 2x. All ACA stones have light performance analysis per AGS reports. I found the Whiteflash generally has more supply and options at the larger carat sizes. HPD would require you custom cut if looking for certain higher colors above certain sizes. Even though all super ideal each diamond does speak to me differently so I would use the custom cutting option as a last resort. Victor Canera’s upgrade policy is also just one dollar more and his settings are amazing. Go to Pricescope for threads on his settings or follow on IG. He also offers super ideal stones and he doesn’t always set outside stones. Those are the only vendors I would consider. Just talk with them. They will each help you find or cut matching stones.