Things to do to build an exhaust - help?

[370Z Purist]

Among other things, I've finally decided to break into the modding community and start doing some things to the Z now that I've decided I can confidently control the stock behavior of the car.

I decided I'd do a simple modification and run BERK test pipes and free up the exhaust a bit. After that, I planned on doing a Gen3 Stillen, but looking at some of the FS threads (especially one where someone in Houston is selling his GReddy Ti-C or Racing Ti), I'll probably stick on a full exhaust, too.

Since I decided to get test pipes as a stop gap measure, buying long tubes like the FI's would either be done by selling the TPs and replacing, etc. or buying the Stillen shorties. Sounds simple enough. I figured I'd mate the TPs to a Y-pipe or similar, then eventually move onto a full exhaust configuration.

So the questions are as following:

What has been proven, butt dyno or actual dyno, to work well with test pipes?

What are my options for Y pipes, besides the EBay pipes?

I plan on staying naturally aspirated for the foreseeable future, so would I want to take a specific route?

My current idea, exhaust only, is to get a set of Stillen headers, linked to BERK pipes, with some y pipe, to a GReddy or Stillen CBE. Unfortunately, I never paid much attention to the actual construction of the entire exhaust assembly, other than looking at power gains and exhaust notes. Most of my experience with exhausts comes from working on boosted Subarus (friend of mine and his entire family owns Subarus).

Help would be greatly appreciated!