I assume they are equipped with the 604-8G drivers? The Zen amp you have will run those Altec's beautifully.  So, from a power perspective, you should be fine.  How loud do you like to listen?

2 Watts will be enough and the amp you have is great.  However, other amps in the Decware lineup could offer a different flavor of sound (and superior sound)  if you feel there is more to be gotten from the Altec's.  Those are great speakers!  I had an opportunity to listen to a pair last year and was really  impressed with what I heard.  

Now, if you really wanted to finish off that combo in extraordinary fashion, get a  25th Anniversary Zen amp  

Interesting