Choice of line all depends on what you intend to do with it.
E.g. what size fish are you fishing for,
Are you casting?
Are you fishing close to obstructions in the water, where the carp could potentially get stuck in?
What is your budget?
Personally, I'm not saying braid is a bad thing, as it has its advantages, but I dont think braid is a neccesity. And the downside is that is can work out to be very expensive. If I had the money to splash out I would buy Power Pro or Berkley Fireline...but I would need 1600m to fill my reels, and this could work out very expensive. Probably over R2000. The only time braid comes in very handy is when you are fishing over say 150m far, and close to obstructions (like reeds, heavy watergrass, etc.) Because in these cases you need to know instantly when a fish is on, so that you can react and keep it out of the snags/obstructions...
That said, a fight with any fish on braid is great. With no stretch in the line, you feel every lunge, every shake of the head that the fish does...but the risk of the hook pulling is now also increased, because there is no stretch in the line to absorb the pull and lunges made by the fish....
If you are fishing conventional, surely you dont need more than the .30 line you mentioned K-Guy? But if you are fishing for the 8-15kg+ or bigger carp, I would get a good strong, high abrasion line, like Berkley Big Game at least 14 or 15lb... The stuff is strong as hell. I've also found Kinfisher's High abrasion mono to be exceptionally strong. Especially when used as a leader... You can cast your ass off without any worries.!
Recently I was in a situation where the best areas to fish was over 350m out. I had to respool with lower diameter line, in order to get to these distances. I only had Daiwa Sensor 12lb line in my bag, and so spooled these onto my reels. I managed to bring in 2 x 10kg carp in on this line... so I'd say the Daiwa Sensor line 12lb and up is also quite strong...the 12lb is .32mm
K-guy, if you're looking for a good leader, you get these small spools of Sufix supple mono in the shops these days. 70m of line on the spool, for about R20... I've been using the 20lb clear line, and its impressive! High abrasion, which is what one wants....
Crazy-bug, I agree, fish are not as put off by visible line as what ppl think. Let me give you an example. The other day I fished a dam that is quite heavily fished. One would think that the fish would be pretty weary of fishermen's tackle, e.g. shiny weights, visible line etc... so I was using coated weights, and my friend was just using plain shiny 3oz weights...this was in crystal clear water.....well, my friend outfished me! So therefore I dont think line visibility would be such a deterrant. Most of our dams have quite dirty water anyway, and some of the depths we fish make visibility even worse....