Mixing different brand cables a good idea or not?

I have mostly Synergistic Research cables for interconnects but have been experimenting with other brands for speaker cable. Is mixing cable brands recommended or just a bad idea? I know many people have said its always a better advantage to get the same brand when it comes to amps and pre-amps. Does the same advise hold true for speaker and interconnects?
Personally, I don't think it should matter much. The advantage of staying within a single brand might be that they are all designed to have similar sound characteristics which might give you an indication of if you'll like another product from their line.

I'm starting to think that some of the companies may have it right for one type of cable and not the other. From everything I've read the design criteria for interconnects and speaker wires are very different so when I see companies using very similar designs for each it seems, at least to me, that they may be great at one type of cable and the other is just to fill a market niche.
Its horses for courses for me; but a full set from Cardas or Transparent etc. will be great without having to worry about matching.
I am in the process right now of trying different interconnects and speaker wire. I bought matching cables from kimber kable , nordost and paul speltz. i have been mixing different cables with each other . i found i like kimber for interconnects best . with paul speltz anticables for speaker cables. The kimbers add bass to the bass shy maggies i have. and the speltz cables i like much better than kimbers 8tc speaker wires . so imho it does not matter.
Some but not all companies can make a great top to bottom line up. So I do agree with both above posts. Personally I think SR is one of the best out there (no I have never heard SR but reading the reviews and friends experiences with them they have very very good cables from power through speaker cables). Me I'm a Nordost fan and will admit they are not for every system or budget.
After so much tinkering with cables and footers to "tune" my system, I have found that it may be best to select cables that complement the timbre of your individual components regardless of the manufacturer. One example, I have a Kimber Select 1021 from my table to phono pre and another from phono pre to preamp. It was the cable that brought out the details I wanted and supplied the air that good analog reveals. I use an AQ Colorado coming out of my CD Player because I wanted the tight deep bass of this cable but also its slightly relaxed high end for the digital signal.

For speaker cables, my experience has shown conductor quality to make the greatest difference. I am a fan of PCOCC copper conductors as they seem to allow for lots of detail but in a relaxed, pleasurable manner.

After getting the cables right, tuning with footers allows that last bit of fine tuning that allows the music to flow. I have had great success with Herbie's Tenderfeet and to a lesser extent, Black Diamond Racing puck/cones. Emperiment, mix and match until you hear that "musical flow" then just sit back and relax and enjoy the MUSIC!

If you are emotionally connected to what you hear you are there!

Enjoy the quest, revel in the accomplishment.