I've been riding for 1 year now and I have a Specialized Secteur with the more relaxed geometry, however as I advanced I want to remove one of the spacers and drop the stem height by about 1/4 inch or more. When I do this what else would I hypothetically need to adjust in order to maximize my bike fit?
Lots of factors will go into this. What are your goals? Why do you want to be in a more aggressive position? Do you have the fitness required to adopt the new position? Do you have the flexibility requisite to make the change? You will only become faster in a more aggressive position if you can hold the position in a relaxed manner. I have seen lots of riders adopt an aggressive position just to look aggressive, but lack the physical fitness necessary to hold the position and end up sitting up a lot because they are sore, or they have a lot of pressure on their hands because their core strength is not on target, and all other sorts of energy wasters. I suspect that many are slower with the more aggressive position because they are less comfortable. In the majority of cases...Comfort = speed.
In the event you do go forward with your adjustments...do not touch your saddle. Your saddle's height or fore/aft should NOT ever move in relation to an adjusted stem.