A little background before my question. I ride with a standard crank set (53-39) and a 10 speed Dura Ace cog set of 13x25. On a flat road, riding solo, I can do about 24-27 mph. One of the club members I respect and get advice from (a former racer at a high level) rides with a compact crank and suggested I consider it. We talked about gearing and chain inches and such and I've been mulling it over. Here's my question. Does it really matter if I mix and match cogs to either a standard or compact? Can't I achieve the gearing I need with either? One of the reasons I ask this is because changing out to a compact can be pretty costly and if I can get the same result with new cogs for the standard, why bother?