I think H SI is a great combination in melee diamonds, no substantial difference between F/G VVS/VS and H SI when talking about very small diamonds, so I would save 500 dollars.
I'd focus my attention on the setting: are the pave prongs properly done? Are the melee diamonds securely set?
I can't tell the difference between my H/I 1 pointers and my D center stone, so I'd save the $500 since I seriously doubt you'll be able to tell the difference.
I was more worried about the fact that it's an SI and not VS... If there are more visible inclusion in such a small diamond, will it make it less sparkly? It is sparkly, I just wonder if a clearer diamond would make it even more sparkly. It this silly?
does this one work. if not, go to the markbroumand.com website, engagement ring, pear shape and then check out the halo ones, I think most of them are.
That is a lovely halo! I'm not familiar with the vendor, but if you call and ask them to check that the stones are all eye-clean, you should be okay. Ultimately it is what is going to make you happy though. There's a comment around PS that rings/stones have to be mind-clean as well. Meaning, if you're always going to be unhappy that you didn't upgrade, then go for it. It all depends on what makes you comfortable.
A more salient question might be whether the upgraded melee are better cut (in addition to being higher color)? I have two full cut 2 pointers that are driving me bonkers on my shank because they have bigger tables than the rest and from certain angles, they look darker than the rest.