I would think for most applications, the standard Solid Disc brake kits would do fine. I have Topline's disks up front and good drums at the rear and it stops fine.
For a more agressive engine than my 1600 with headers and webers, i'd go with disks all around.
If you're looking for a lot of stopping power, then you can work on collecting parts for a 944 brake conversion. You will have to convert to a late suspension, though.
There's alo the Kerscher (CSP) kit, which looks pretty nice to me if you dont want to convert your suspension or if you dont have patience.
Then there's my favorite system, which I'll probably convert to one of these days, if I get a T4 that can really put the power down. Remmele had a 996 Brake Kit that Aircooled.net sells. You send in spindles and they machine them to use the Remmele kit. It's also a pretty expensive kit, and dont even ASK about the kit for all 4 corners
That's the way I see things. There are people out there who know more thn me when it comes to brakes, and I'm sure they'll chime in.