Yes, it's possible, but at least one of the sites will need a public IP address that doesn't change. The encryption licensing for the PIX is a free upgrade as long as you're not in a restricted export location. It's available from Cisco's web site via form you fill out at this URL:
https://www.cisco.com/pcgi-bin/Software/Crypto/crypto_main.pl?prod_refer=pix3des
You don't need any router other than what you'd need to provide the Internet connectivity to the PIX, since the PIX doesn't have any WAN ports (i.e DSL, Cable, Serial, ISDN, etc.). Cisco also has sample configurations for what you want to do at this URL:
http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_configuration_example09186a0080094761.shtml
Good luck!
