The S710a was reported to be exclusive to Cingular, so as far as I know, Cingular and allied outlets may be your only source for this phone. Also, if this is the case, you may be SOL for finding this phone unlocked, unless you take it somewhere else after purchase.

One thought, realizing your original message was posted in December of 2005, I understand the S710a is nearing the end of its projected service life, and even if this isn't true, newer phones are being released all the time. I myself am waiting for the replacement for the S710a (and I do NOT believe this is the Z520 or any current SE phone, at the moment).