Usually the scavenging effects on the 4 cyl are needed if you split it right after the CAT you could potentially lose some performance (that's why H pipes or X pipes are usually an addition to the dual exhaust on the V8's.
You could do something at the rear of the car if room using a single inlet dual outlet muffler. I always think its weird in the winter though when you see 90% of the "steam"/exhaust fumes coming out of one tail pipe and nothing out of the other. the whole will flow the path of least resistance.
the FSworks stealth exhaust is one of the best. you could go with a 3" from Trubendz and then add in a large and long resonsantor but would most likely be more costly than the FSworks Stealth exhaust.
2001 ZX3 2.0L Zetec-
Hatch Nation #42
Going through Rebuild See "The TICK Build Thread" for details (http://www.focusfanatics.com/forum/showthread.php?t=289168&referrerid=62897)