Summit makes good products, all depends on whether you want the look of a nice aluminum box though As for the sequentials, I would go with the ebay kit. I saved over $200 buying my HID's from an ebay store and they are just as good as any other 8000K kit.
Personally; I'd do the sequential tails. If you're not racing and don't really have a need to relocate the battery then I don't see why you need to relocate it. I've also heard of a lot of people having some issues once they've relocated it.
I have to agree with Lefty..... to a point. What are you going to do with your car? Are you going to track the car at all, or is this a car for looks? If it is just a crusing car that you want to look good, get the taillights. If you plan on doing some serious track use with it, then go with the relocation kit.
I'm with Lefty, unless you're a dedicated racer I don't know if I'd do it. Sequential tails are cool though, I'd do that. You're NEVER going to be the fastest, so why not try to make it look a little nicer?