Hi Paulie,
I don't quite undestand your question. To paraphrase, I think you have two machines currently (one WSS, one SQL) and you need to move to configuration with 3 machines (2*WSS loadbalanced, one SQL). I think the mention of SPS (Sharepoint portal Server, referring to 2003 version) is just off-shoot and you meant WSS 3.
If I got the start point correctly, you are already technically deployed as farm. The only non-farm option (standalone) is using SQLExpress (or Windows Internal Database) and that is always on the same box as the WSS/MOSS. If you want to be really sure, you can check the value of regkey HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Shared Tools\Web Server Extensions\13.0\WSS\ServerRole. If it is SINGLESERVER, that is the standalone, everything else (WFE, APPLICATION) is farm (needless to say, just changing this key on the fly only means problems so don't do it).
If that is correct, all you need to do is to add another WSS WFE to your farm and set up the load balancing. Most likely you will also need to set up the Alternative Access Mappings.
if you have a standalone server, the supported way is to take backup of the standalone, set up the desired farm and restore there.
JP