M-AUDIO Firewire Solo - Firewall cable quality?

Any FireWire cable you can find that meets the spec will work.  So if it's a legitimate FireWire cable it will work.

The thing to be careful with when using FireWire is to heed the warnings not to hotplug or hotswap when using a 6-pin cable (a cable that supplies both data and power) while the computer is on.  It is possible to possible to insert the plug crooked and short a data pin with a power pin and end up frying your FireWire port in the computer or fry the FireWire circuits in your device.  The manual for your FireWire Solo should have warnings about that.  There's a reason.  The FireWire plug isn't designed sufficiently mistake proof.

If your computer has a 4-pin FireWire port (like laptops do) then you're fine to hotswap.  A 4-pin FireWire port supplies no power and can't short when plugging it in.  When using a 4-pin cable you'll need to plug a wall wart in to your FireWire Solo.

I'm using a generic FireWire cable with my M-Audio FireWire 410.  I don't know the brand of cable.  It has no markings identifying it.  I needed a longer cable than what M-Audio supplied.  It works just fine.

If your FireWire card includes a 4-pin connector you can experiment with using a 4-pin to 6-pin cable and using the wall wart to power the FireWire Solo.  Some people say using the wall wart is better than using the FireWire bus power.  Supposedly cleaner power or whatever.  You can try and see if you notice any kind of sonic benefit when using the wall wart vs. bus power.

If your card doesn't have a 4-pin connector you can use a 6-pin male to 4-pin female adapter.  Then plug in a 4-pin to 6-pin cable, and use the wall wart.

What you don't want to do is use a 6-pin port and the wall wart at the same time.  You'll be powering the FireWire Solo by both FireWire bus power and wall wart power.  It's probably not going to like that and might damage it.