I've started looking for a small device I can either carry in my pocket or
clip to my belt that will do the functions I need it to....a combination
cellphone/web browser.

I have a Cingular phone now and would like to switch to something like a
Blackberry or a PocketPC.  I'd like to get the latest and greatest unit
available.  Specifically, in addition to using it as a cellphone, I need
good unlimited web access, and the screen needs to display webpages that I
can actually use for my business.  No, I don't want to use my laptop.
Specifically, I need to:

1) Get my POP email from both my Bellsouth email account and also my Yahoo
Merchant account.
2) Send POP email from my Bellsouth email account.
2) Browse the web to my Yahoo Merchant account, log in, and check orders
from my Yahoo stores.
3) Browse the web to my product distributor's website, log in, and place
orders online.
4) Browse other websites.
5) Use as a cellphone.

Will Cingular work with either the Blackberry or a PocketPC like the new
Treo 650?  What's the best device out there that will meet my needs?   Is
there a preference of one over the other?  Speed of internet connection?
Speed of device processor?   What kind of Cingular plan will work with
either of these types of devices?

I would appreciate any advice or recommendations.  Or answers to any of the
above questions.

Thank you,
David