If you're looking to get a big rock and want to save some money I may have a suggestion.
Engagement Rings | Wedding Bands | Jewelry | Diamond Nexus Labs
I'm not affiliated with them BUT I've seen the quality and clarity of these stones and they're excellent. Basically a synthetic diamond that has all the properties of a "real" diamond, including hardness, without any of the flaws. You aren't able to choose a clarity because all of the diamonds are FLAWLESS. These stones also come with certification from the american international gemologists. Best of all, the price of the ring is much cheaper due to it being a manufactured part rather than a rock that's been mined, ground down, and polished.
Ofcourse if you absolutely NEED a diamond stained with the blood of some African miner your local jewelry store will do. =)