asterisk users - Jun 2005 - ASDI Programming through an ATA/SIP device?

As I've said before, I have a number of phones that I've converted
from Packet8's Virtual Office to work with my Asterisk stetup.  They
are basically Leadtek 85XX SIP devices with Astra 390 phones
connected.

I've been investigating reprogramming the Astras to say something
other than "Virtual Office powered by Packet8" but when I try ADSIProg
I get something about CPE not being available.

I'm afraid to say but I think that I'm going to have to get a Zaptel
device to get the phones programmed (a single port that I can plug the
phones into and then have them call the programming extension, maybe)
unless there's something that I'm missing --- can I program an ADSI
device using a SIP interface?

Thanks!
Hatto n