Fat Nick
Footballguy
I'd honestly go the other way...Platinum is barely more than gold these days now that the price of gold has gone up so much. Plus, Platinum is a much harder metal. It will wear better, and if you have a platinum engagement ring, the platinum being harder will help the stone stay secure better.I would recommend going white gold instead of platinum and put as much of your cost towards the center stone. That's all anyone cares about.
I'll add that I'm one of the few people I know who went the designer retailer route. I heard so many horror stories from folks going the local jeweler or custom jeweler route. People having their rings stolen, getting bogus diamonds, getting sub-par craftsmenship, etc. I paid a little extra for a Tiffany ring and haven't thought twice about it. They clean it, and do polishing for free. They basically are your ##### for life after you buy a ring from them.