It's going to depend on what apps you're running. For standard day-to-day use, you're not going to notice a whole lot of difference. If you're a Photoshop user, then frankly the extra RAM will make more difference than the CPU if you're dealing with big files.
Overall, if you have the 1.83, I really don't think it would be worth upgrading to the 2.2. Not enough performance hike for the dough.