I have a question and it seems like this would be a good place to ask it. I have been searching high and low to find a replacement for the stock crank on my bike. I found an FSA Gossamer on eBay and the price was right. The stock crank has a 42 tooth middle ring, the FSA has a 39 tooth. Will there be a noticible difference?
Are you going from a triple to a double or something?... Apart from buying a new crank, I'm not sure what you're trying to accomplish. (I don't know if the Gossamer cranks come in triples)
There will be a noticeable difference switching from a 42 to 39t chainring, but if you indeed are going from a triple to a double, then your next concern should be your shifter. You can either swap out your current shifter for a double indexed shifter, or just physically block out the third indexing in your current shifter.