IPsec VPN connect with MS Proxy Server?

Basic details:
Company 1: SonicWall SOHO3 protected LAN with DSL WAN connection. Static IP on SOHO3. Win2K clients behind the firewall. IPsec for VPN.
Company 2: MS NT 4.0/Proxy Server 2.0 LAN with DSL WAN connection. Static IP on external adapter. PPTP for VPN.

Is there a way to implement a VPN with these two seemingly incompatible VPN application/devices? Here is where my thoughts were leading: An add-on for Proxy Server for IPsec. A PPTP work around on the SOHO3 or Company 1 client systems. Open UDP/TCP ports 500/1723 on the Proxy. A 3rd party software firewall that will allow this VPN without interfering with the Proxy Server or costing a bundle.

Thanks in advance for any help.