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