Load Balancing Using Multiple PPP Links?

M@W asks: "I currently run a Linux box (Slackware) in the office to handle e-mail, Web serving, SQL serving, dialup, print and fileserving, and it is connected netwise via a permanent modem. We're shortly opening another office a few kilometres away, and will need network connectivity. Since ISDN is so costly, I was planning on running two or more 33.6k modems at each site. To distribute the network traffic properly between the links do I need to be running something like EQL or EQL-plus? Since both ends will be our private networks, can I just assign IP's to all modems and set up the routing tables to use all links? Has anyone else done something like this? (Another option would be to use cable modems and a Virtual Private Network link, as they're only $59AUD per month (flat rate), but they don't allocate static IP's)"