That's a pretty hard to answer question. First what do you have? 2 piston or 1 piston fronts? The 2 piston ones are the "big brakes", you should have them on a 1Gb.
If the brakes suck it's probably because they aren't even working to the maximum of stock potential. I'd be willing to say most brakes even on performance enthusiasts cars aren't in 100% condition. Most people neglect them until they start squeeling or grinding, especially out back. I know I'm guilty of this from time to time. I never drive with unsafe brakes and they're not lacking under normal driving but if I push them hard I know they're not 100% of what they could be, which would be right on par with 90+% of the cars out there.
Taking them apart and cleaning the slide pins and calipers and then lubing them with some proper brake lube would be a good start. Fresh cheap fluid performs better than old performance fluid. A thorough brake bleed and new fluid should help alot. Same as an engine, you do't start swapping turbos and cranking the boost until you've done a tune up and the engine is running right.
From there how much extra stopping power do you want? Some good pads and SS lines along with fresh fluid should make a noticible change. There's been some threads on here regarding performance pads on stock brakes, look them up for some good brands.
Other than that you'd have to start searching for actual rotor and caliper upgrades. I have AEM larger rotors on one car. They use the stock caliper. The next step up from there would be a 4 piston caliper, preferably with quick-change pads. Stoptech, Brembo and Wilwood are some good names. Wilwood, according to their site, doesn't offer a 1G brake kit tho. The others I looked at quick but didn't see a quick guide. People have done custom stuff before tho, do some digging, maybe send some emails to some companies and do some other searching, there are other brands out there too.
The next step after that is going to be to get custom. Do some custom machining and fabrication and you could put in somethig like 6 piston fronts on 13"+ rotors, dual master cylinders with an adjustable bias bar, upgrade the rears to some high end 2 pistons or even 4 on 12"+ rotors. You'd need all new lines and brake pressure guages to get it all setup.
Costs would range from a few hundred for lines/pads/fluid to real money ($3000ish) for a brake/rotor upgrade to serious money and time (probably $8000+ and a ton of hours) to go all out. On a Porsche 911 turbo the carbon/carbon brake option is like $25,000, that's on top of the usual high performance 4 piston brakes. Stopping costs money, how fast do you want to stop?
