I do not currently run webmin on my Qube, but I did in the past.
sure, it was not very fast because it was generating everything
dynamically with perl, but it did work just fine.

My qube has 128MB of ram, not sure how much of a difference that
makes, but another Qube I am helping a friend with only has 32MB, and
I am almost certain webmin would be much slower on that one.

-Justin