did anyone bought their proposal ring from tiffany?

Here begins my headache moments. Although my gf once told me to decide on the diamond ring, I am unsure if I should go for those ready made well-known diamond ring brand (like Love&co, Hemera, Le Lumiere and etc) or should I go for those customize diamond and ring (like Brian Gavin, Audrey, Wah Chan, JannPaul and etc). Ladies and guys thinking may be a bit different you see... guys are more to technical stuff than just looking at brand (specs, performance, etc) while ladies usually go for brand (Tiff&co, Love&co, etc).

Any opinion or suggestion based on the above? If I were to order those diamonds from Brian Gavin for example, you think it can fit my budget and enough time to do the setting as well? Thought of JannPaul too but I don't know if can fit my budget as well. Worry if I go SG then end up with failure. Hope all the sifu here can give me some guidance.   
**Sorry to keep this one so long. I just hope my scenario here can help others as well when comes to decide on the proposal ring** 

Thanks for your view! That is great that you view it that way. Because I think diamonds play an important role for the ring. for the same budget, you will be getting lower specs for a branded diamond ring and getting a better specs in other customisation shop. My consideration is more to the customisation shop like Wah Chan, Eymayco, JannPaul and etc. But I do want to get what best for her and the ring she will like most. How do you think I can find out which one she will prefer from my girl based on your opinion? Ask straightforward way? 

I pakat-ed with her siblings on the ring design and the overall proposal. When the day came, she was "angry" with them for being such great actors and actresses all the while haha!

Oppss... Guess I can't do that now. Hahaha. I don't want to involve the siblings with my own reasoning. Plus, she has 4 sisters (2 married), guess will be a bit to obvious if they ask suddenly. I think close friends or colleagues might do the job for me. But thanks @annann91 with the suggestion!

Based on what I know about my gf, she might look at designs more than just brands (based on the way she shop for clothes). Thou sometimes might conflict with this (branded handbags due to better or classy designs). I just hope she gonna answer them that she likes design and diamond better than just brand! *finger-cross* Then, I can decide on my next step for the diamond rings. Will keep you guys update... 

Besides those famous ones outside MY, any suggestion that I can get a really good diamonds (H&A)? A place where at least able to show me the diamonds and other scope (Ideal, ASET) than just the normal H&A scope. Yesterday I went into Eumayco and he shown me his best diamond based on the minimum diamond spec I provided to them. Here is the GIA cert number: 2266424612. The cut score is 94.1. What minimum score will you guys consider it as good and acceptable? I am sure it is hard for you to go to a shop and just look for a 100% score diamond cut. But the last time I entered Le Lumiere, 2 diamonds also with 100% scores. Such an coincidence...

Yesterday, my gf brought up about a proposal ring thingy. Her best friend asked her out to help on wedding gown selection on Saturday and they had a conversation about proposal ring and wedding band. Then she shared it with me about their conversation and gave her honest opinion about the ring. She said she don't want those branded ring coz is too costly and what she prefer is the design of the ring ! Hahaha. At least now I don't need to worry if I need to go for those Le Lumiere or Love&co diamond ring. Can now focus on searching for loose diamonds and go for customise ring.   

If i send my diamond for setting, should i leave the stone with the jeweller? Or i should keep it once setting is done only give them my diamond stone?

Afraid they will swap it with another stone.. mine is GIA, i know there's laser number on the girdle but i guess its not hard to fake it? Since it will be with the jeweller for about a month.

do any1 hav experience to buy diamond oversea to hav tax refund to enjoy better price compare to buy locally? pls share if it is a good idea to do so.