The Price for the Sequential the cheapest I found were $149 and are a plug and play. You can find them at the following sight.
http://www.mossmustang.com/home.aspx
But for the chase they are not a plug and play but are not that difficult to install and cost $120 plus $9 s&h.
The toughest part of the chase is trying to get a power wire to the back through the rear seats but the results are awesome. You can get the chase from the following sight as well and see the difference between chase and sequential.
http://www.meter4it.com/2005_Mustang.htm

 

You do realize that the Meter4it has the options of Chase, Sequential, and Normal? They are not just "chase"...

 

True thats why I went with Chase because it was cheaper and gave you those three options

 

I agree with Sarah's observation. They look the same to me. The chase seems to be moving faster if anything. They are cool...but to me, they are the signature trademark of the Mercury Cougar. Cougars are terrific....but I'm more a traditional type. But that's me!

 

Thats cool everyone has their taste in what they want to do to their rides. Thats what makes us all unique with our rides.