Good afternoon.
I think Yaffle was asking about a Spey type line.

And not one of the special types of lines suitable for Double rod casting.

The Scandi or Skagit are very special lines which require a whole new learning curve for someone starting in Doubles, which is one of the reasons why I suggested a Short Head Spey line.

Once the caster starts to understand and feel his beautiful Double rod, then if he or she wishes, then explore the other forms of casting...which he or she will...

"Are there some spey line brands better than others? What would you spey guys suggest?
If there are many good brands is there certain brands I might want to stay away from?"

I was not going to answer this, you could consider an Airflo Delta, good core, smooth, great coating on the line.

"Is there a common leader wt and lenght that would make a good anchor for this rod size?"

Generally, the leader length will be governed by the fly size, however it is ideal if the butt section of the leader is about 75% or more of the tip of the fly line.

In your case with a 13foot 8w and trout/salmon or steelhead sized flies I, myself would start with 15feet, and would outwards as you developed casting.
The above is if you are using a shallow running or surface fly, for a deep sinking fly, start to reduce your leader length, till you have a 'good' cast.

To start, always start to understand this Double World with a floating line and floating fly, its far easier.

Once you master and start to feel this Spey casting (excitment), then you can expand your ideas and casting to leader lengths like Mike Thomas has suggested and then enter the World of sink or intermediate leaders and or tips.

ps, I now use Shooting Heads, for both the salt and freshwater applications on rods larger than the 5/6w 12footers.

Kind regards,
UB