Hmm, well sounds like your on a road bike and technically upgrading every piece in your whole system would help. I had the same concern with my mtb after I decided to stay with v-brakes. I upgraded the pads, cables/housing, and levers and how they stop as good at mechanical discs, if not better.

I would suggest adjusting them first to see if you can get the results you want and making sure the whole system is perfect (cables and housings are smooth, etc.). The next step would be to upgrade the second cheapest thing which would be cables/housing or pads. And if that doesn't work, upgrade your cables/housing and pads.

Kool Stops are good for everything and I have heard good stuff about Swiss Stops, although I've never used them. I would also suggest spending more money and using nicer cables/housing. Nicer cables/housing grants you one of two main upgrades (or both of them): smoother operation (via PTFE/Teflon coating, minimization of compression, etc.) and/or longer life (by being fully sealed).

Of course the last resort would be upgrading the brake body, but that is the most expensive and it will definitely be better, but would it be worth it? It all depends on whether you want good enough to make you happy, or the best ever. For my mtb, I've made my front brakes as good as possible, but my rear is just semi-sealed.