I have many different Impact stands from the (2)8ft air and (2)9.6ft air cushion to the (2)convertible boom stands and 3ft background stand. (The 9.6ft is a great heavy duty stand.)
They aren't the greatest, but they are pretty good for what I do.
(Although the converible booms are aweful in my opinion.)
If the Impact does the job, why trade them.
Today it's only a Speedlite and maybe umbrella, maybe tomorrow something more.
I would think after selling and shipping your old ones and buying the Amvona's and paying for shipping that it may not be all worth while.
Unless of course there is a huge weight difference and you are always on the go with them.
I say keep the Impacts, but hey that's just my 2 cents.
Perhaps someone who owns the Amvona ones can chime in...
-Mario