Will an external soft start device limit current?

Why are you getting them . . . I mean, what is the purpose? Are they "soft starts," or VTL Pod Mods?
I used the VTL Pod Mods for awhile on MB-450's when I had them. I think they are designed more to protect your electrical circuit than the amps. I found I didn't need them and sold them. I don't believe you will need "soft starts" to protect the amps.

I did not ask for them, the dealer is sending them at no charge. I will have to see if I even need them. He did state I should use them so I don't blow circuit breakers. Did they effect the sound in any way?

If you're not blowing circuit breakers now, which I don't think you seem to be, why use them (whatever they are)?
Whether they will affect your sound, I guess you'll find out when you get them.

By limiting current on turn-on, soft start circuits greatly extend the life of tubes. When cold, the filament in the tube has a much lower resistance than it does at operating temperature. That means that when you turn the component on, there is a sudden surge of current and very rapid heating of the filament. It is this thermal shock that is bad for the tube. If the amp has a tube rectifier, this acts as a form of soft start for the rest of the tubes.

Therefore, a soft start circuit (e.g., a series-connected thermistor) is most useful in an amp with solid-state rectification. The thermistor will not fully conduct current when it is warmed up, so it can, to some extent, reduce the current flowing into the amp after it has done its job. I personally don't know how much of a sonic effect that will have, but this is the trade-off.