If i read your comment correctly you dont want to change your primary number and the other 9 lines right?
If that is the case, and you need a gsm phone, im guessing because you cant get reception on sprint phones? Any way, you can always port your main number to a GSM Carrier like Cingular. In regards to your other lines, i believe they can do that also, but you may want to ask a rep. All you need to port the number is your current cell phone provider's account number. Then the cingular rep will take it from there.
I have about 10 lines through Sprint, but one of my business partness told me in no uncertain terms that it was a pain in the *** for people to get in touch with me. I told him I'd get a GSM phone (prob Cingular) but it is a major commitment to change my primary cell number and most of my other 9 or 10 lines. Any suggestions?