There is no way, sorry. SOHO is based on KDE, Standard on xfce. You could try loading all the KDE packages, but you are kind of defeating the purpose of Standard then (a nice small fast distro with a lighterweight environment). If you really want SOHO I suggest you install it. The easy way is to get yourself some extra partitions (if you have a large enough hard disk) and dual boot either SOHO or Standard. You can easily share files between them, if need be.