I have Virgin Mobile and I would like to know if I could buy an unlocked phone (env maybe?)and use it with with my current network. If so, is there certain phones that work better unlocked than others?

You can, but it’s not easy, and it’s likely to fail. Virgin is an MVNO of the Sprint network, which is CDMA. You can’t unlock CDMA phones. You can try to have it reprogrammed, but Sprint is notorious for only allowing approved devices on its network, and that includes MVNOs (sorry for all the acronyms).

unlocked phones usually refer to those on GSM networks, which in the U.S. means T-Mobile and AT&T. They use SIM cards. CDMA networks like Sprint, Alltel, and Verizon do not use SIM cards.