ESN question

[jpwhre]

So I called Sprint this morning and was approved for 3 lines of service. Asked to have my cricket # ported and everything. I have been searching ebay for while now, and was wondering if I got a phone with a clean esn, even if it is on tmobile, att, or anyone else (not cricket) could it be activated with sprint, or do I have to find a sprint phone specifically? I am sooooo tired of a lagging line of service with a connection that is less than........... Well, less than. If I can use other carrier phones, what do I want to avoid besides the mentally handicapped Verizon line up? CDMA or GSM, doesn't matter which one I get. As long as I can use enrgy rom.