Does using same brand cables improve performance?

You're likely not do much wrong if you go for one brand and more specifically one series of cables and cords to wire your entire system. Having said that, I do agree with the previous posters, to quench the best out of your system, carefully mixing brands and/or series may get you closer to your personal sonic nirvana. In this regard, note that some renown companies will actually manufacture only cords (LessLoss leaps to mind) or no cords at all (e.g. Townshend) or no speaker cables (e.g. Cicable). And sometimes, a manufacturer will actually tell you they introduced a new cable on demand just to be able to offer a full product range, aha... The risk of subscribing to the joyful art of mixing is that you may pile up various unused cables after a while because even if you do audition each new one, there will always loom another you'll want to try (luckily, helpful Audiogoners can mostly be found and be at your service to get rid of such pile ;^).

Experimenting with cables will definitely be a well worn path as there are literally hundreds of options, especially when dealing with seperates. Some applications work better upstream while others work better between the preamp and amp. Mixing and matching is also preferred by most, me included after you become intimately familiar with your sound. However, some swear by same brand throughout - network cables sometimes work better this way. There are also tons of cables that do a fine job at all types of price points - then throw in listener preferences - Wow! Karelfd is spot on - I have a pile of cables that are not in use or see some playing time on occasion - usually when I get bored.

As Mechans stated Boulderdash!! Most people mix and match components made by different audio companies, why would anyone believe that to get the best sound you would need the same cable manufacturer's cables when in most cases the components are from different manufacturers.

When you mix componets from several manufacturers it's not unusual to have to deal with 'hums and buzzes' and minor problems of all different sorts. Mixing cables can likewise be a challenge with the benefits of one cable cancelling out the benefits of another. Manufacturers have certain design characteristics that result in a synergy when used together. I have validated this several times over using clusters of componets from Audio Research, Jeff Rowland and in lesser systems from Rotel and NAD. Mixing these brands never produced as satisfying a result as keeping the brand consistent where possible.

As a cable manufacturer, it may come as a surprise that I agree with the Balderdash comment. Each interface is its own problem and therefore may need a unique solution. I wouldn't go so far as to say that you can put a syrupy, rolled off cable together with a bright cable and get anything coherent. But each step in your audio chain is likely to present a different challenge in terms of mating output impedence with input impedence, as well as potential phase related issues. It is also not true to assume because a manufacturer's interconnects are great that therefore their speaker cables will be great too. To be ompetitive in the cable field these days you really need to come up with something of a breakthrough, not just apply conventional wisdom. The breakthrough that makes your interconnects special is unlikely to have the same, or perhaps any, relevance to speaker cables. For each interface in your system you need to find the cable that enables the music to be a combination of lively, well-balanced, with nice black backgrounds (these are the things that will be right when you have the interface right). The rest of the characteristics of the cable are the house sound and you either like it or you don't. Lack of liveliness, phase related anomolies (which we perceive as tonal abberations) or grain are an indication that the cable is not a good electrical match for the particular interface. All of tyhis is just my opinion, of course, and I love it that we all perceive the world differently.