Don't know if there's a price difference between the vendors and Pfadt themselves. I've had dealings with Apex and JDP. I wouldn't hesitate to order from either of them again.
One thing though. If you're considering lowering your car as well, it would be in your financial interest to order it all at once. The Pfadt stage II is both sways and springs and saves you a good bit of $$. You might be able to swing a deal on the endlinks while you're at it. Never hurts to ask.
