triple ex usually will have some form of hearts and arrows cut.
its good to know the 4Cs, the HCA score, see it under the idealscope and compare it to another diamond
however, the most important bottomline is: you don't want to pay too much for a stone.
the rough "value" can be calculated in the washington diamond calculator. HCA scores will up and down the value a little.
set a budget, then go for what you want. if you like size, sacrifice some clarity or the cut. if you like nice reflectivity, you can give up a little on color. most people can't tell the difference between a D and G or an IF and VS2. But they can tell the difference between 1 and 1.2 carats
So if you diamond is worth, say 5k on the market but you paid 15k for it(profits/costs/brand names etc) then thats lousy value.
But if its worth 6k and you paid 7k for it, then thats much better.
a diamond is a STONE. there is NO difference whether you buy the same stone from Soo Kee, Larry or import from Blue Nile. Say 2 stones are the same. 1.02C, F VS2 tripleEx. One has HCA of 1.3 with a perfect H&A and the other has HCA of 1.8 with asymmetrical H&A and minor light leakage. But the first cost 17k while the second cost 12k. I would choose the second.
So before you decide on HCa, heart and arrows, idealscope and the 4Cs, ask yourself the most important question: Am I getting fair value for my money?