Research very carefully before you purchase.

They can be nice if the work your doing falls within the limitations of the SWPS.

D1.6 structural code for stainless has a section devoted to development of prequalified procedures.  This may be a better course of action.

Each SWPS provides a specific thickness range, shield gas selection, amperage/wfs ranges etc.

Many would argue with Aluminum work that it is much better to qualify your procedures to prove your process is under control.