I did this very thing. Stainless works headers, Gesi cats, into the stainless works aftermarket connect leads. These have a 3" connection point to the rest of the exhaust. then, I installed the Corsa Double H pipe, that also has 3" in and out, and uses clamp on adapters to meet up with the factory axle back. This setup allowed me to get rid of the factory neckdown, and maintains 3" all the way back to the active muffler section.
So, just get a set with aftermarket connection leads and a hpipe or x pipe with 3 inch in correct?
Well, you still need to choke it down after the H-Pipe to meet up with the active exhaust muffler section. This is why I went with the corsa Doube H, because it has the adapters to connect to the OEM pipe size at the mufflers, but has 3" ID slip joint at the inlet side to accept the 3" OD of the connection pipes. The Stainless Power/Works connection pipes have a flared section towards the H-pipe, but were long enough that I could just cut that off, and use butt clamps to connect to the Corsa Double H.
