I just bought the engagement ring last week, will be able to collect it by next month. Actually clarity is not an issue at all. And I do think that colour makes a lot of difference, even I can see yellowish at the side of the diamond with grade F. And I found out that purchasing in Singapore is much much cheaper than in Malaysia. Carat wise.... its really depend on your budget. Nowadays diamond has standard quality like 3e and ideal cut. So most likely you will consider color most of the time.

Good luck in choosing the only one ring.