GIA cert number will be useful. Do you have it?

Also, may I know which shop/vendor offer you this package?

The proportions offered are good. Read this:
http://www.prosumerdiamonds.com/how-to-pick-diamond/

Based on the numbers, the diamond should perform well. And XiuKeong also calculated HCA score of 0.9, which makes this stone a candidate to consider. For the price of RM 8,500, personally think that it is a fair price for a brick-and-mortar shop. Don't think other brick-and-mortar will be able to beat this price. Wah Chan is famous for competitive price anyway. Btw, 0.46ct should be close enough to look like a 0.5ct. 

The next thing to do (if possible) is to request for the Hearts & Arrows images or any other images. If the actual diamond is in the shop itself, even better, you can view the diamond from the top and from the bottom, to take a look at the Hearts & Arrows. Be sure to take a good look at the diamond and see if it looks nice to you (you know, fire and whiteness, things like that). Lastly, ask them for the location of the inclusion (The crystal, the feather, as stated in the GIA cert). You don't want something that is too easy to crack.

Good luck and enjoy your diamond hunting. 

Well, just checked on Audrey's for price comparison. You can probably try to negotiate your price further down for that D colour VS2. Perhaps to around RM 7,800 - RM 8,000? However, do note that CUT will make a big price difference, since the proportions looks good, so what's left is to view the actual diamond. So, if you can see the hearts and arrows clearly and you like the diamond appearance, then do negotiate with full force.

Another thing to note is that the ring setting itself does play a part in the pricing. You can check with the salesperson what material are they giving. Is it 18K white gold? If yes, then it will consists of 75% gold + 25% others. You can then check with he/she what is the 25%, does it contain palladium?

On a side note, for your price, you can try to check with iDo Jewellery and see what price range she offers you. She does provide ASET, H&A, Actual Diamond images.

For even cheaper option, you can try to check with Tailored Jewel, which is currently running a promotion for 0.40 E VS2 + 18K White Gold Ring for RM 5,900. Your diamond is bigger and has better colour, so the price should be higher.

Hope this helps. 

Great to hear that! Chosen the ring setting?

Hmm, no 4 prongs selection? Anyway, how is the variety of ring settings available in Wah Chan?