Keep in mind that if your steering geometry is correct now, then using lowering springs will make it incorrect. Drop spindles will alleviate this issue. Also, the wheel fitment issue is a good one, it stinks to buy and install parts to work with your current setup, and then decide you want to change the wheels that your were previously working around.
Weight via motor upgrades also affect stance. We put a new power plant in the car last winter and it dropped the car an inch and improved the geometry????? Kind of hard to imagine, but it did.
Good luck.