Welcome to the forum bud
ton of info here and help from everyone. If you're looking for a loud exhaust on a budget then it's gonna be tough. HKS is pretty loud but expensive. Fast intentions is sweet but there is a long waiting time for it, but well worth the wait. Top speed has some true dual exhaust that are pretty throaty but not too sure about the quality of the exhaust like durability, welds, etc. YOU GET WHAT YOU PAY FOR. Very important to keep that in mind when purchasing mods for the Z. I personally like the berk exhaust because it fits my budget and preference of sound. Also it's important if you're gonna be able to tolerate a loud exhaust if you're Z is your DD. Also if your girlfriend or wife will allow you to have a loud exhaust.
That being said you sound also YouTube different exhaust on the Z. Some videos have exhausts paired up with test pipes or high for catalytic converters. They alter the sound of the exhaust with a little hiss or deeper growl. If you like that kind of sound then I'm pretty sure you could find something you like.
If you want something loud and sporty while still being on a budget then you should research AAM short tails. They're pretty loud and if I'm right they're about $400. Add some test pipes, maybe around $300 I think I'm not too sure, and there you go. Nice loud exhaust for your new toy.
Hope you find what you're looking for