Exhaust System for 7A-FE, Ballpark prices Options

[Espo]

So I've had my Celica for over a year now, and about a month ago I noticed my exhaust manifold had started to crack, right in the middle. I would say between the number 2 and 3 cylinders but I'm not sure that's the correct terminology. (Cylinder numbers go in order of firing order, right?)

Anyway.

Two days ago, I start up my car, and nothing sounds off as it idles. And then I start driving, and I hear a rattling sound much like that of my buddy's Firebird. The problem with that? His Firebird's catalytic converter is hollowed out. And now mine is too, it seems. Same sound, and my engine sounds a tad bit different at certain throttle positions or rpms.

Thus I'm going to replace the entire system, headers, hi-flow cat, and exhaust, but I have no idea where to start as this will be my first-ever performance related modification to a car. So I have a few questions.

Firstly, how much is a hi-flow cat going to run me? I hear prices in the range of $200 which isn't too bad.

Secondly, I have no idea how an exhaust system runs under the car. I know where my cat is and what it looks like, but after that, nothing. So what will I need for new exhaust piping? I would love to order a Tanabe Medallion but they only come in packages for certain cars. Can I just buy a cheap Medallion for say a civic, have a shop cut the old piping and weld new piping in for my car and call it a day? Or is there something more to these to get the correct sound out of it? I want something with a deep hum or a low rumble to it. My friend's STi has a Blitz Performance system that sounds great, but I know the 2.5 Boxer doesn't necessarily sound like a four cylinder.

Thirdly, are there any tuned headers for a 7A-FE? I'm scared to look on EBay, I always see people going "don't get cheap EBay headers" but I have no idea where to start. According to my Dad, I'll need tuned headers (each pipe being the same length as he explained it) in order to see any performance gains from it. If there aren't tuned headers I suppose I could go with...untuned? headers but either way I need something to replace my manifold before it splits completely.

[mgnt232]

The only "made" exhaust systems for our cars I believe is the greddy sp2, but they arent made any more and could cost like 700+ for the cat back. (or at least one auction i saw)

And if your not doing the work your self, go to a shop first! and make sure they can bend piping, and will do the work for a reasonable amount. I know when I was planning on a cat back, I didnt know that no where around me bends piping, so I was left with a new res. and muff. which still gave it a nice sound.
But exhaust if you or who ever is doing it, doesnt do custom all the time, it can turn into a big "hack and weld" experiment.
Headers are cheap, but you do get what you pay for, mine came a foot short, 1/4 wide, and all the holes needed to be drilled out.
I would be prepared to spend at least 500-600 on a "full exhaust"