It all depends on which way you want to go. (You have a few choices here

)
Which carrier ? would be the first question. All 3 majors have a BlackBerry BIS package available so really a question of which one you prefer.
Secondly BES or BIS ? (
BlackBerry
Enterprise
Server or
BlackBerry
Internet
Service). If you are just a single user not wanting to connect to your company server then BIS would be quite adequate. On the other hand, if you want to use the device on a corporate server then BES would be the way to go.
Get back with answers for those 2 questions and we will go from there... Or if you want further information just ask...
Hope to hear from you soon...
KR
Greg Myers