I have been experimenting with soldering sterling silver wire loops together and then hammering them flat. So far I have had luck with a cheap little butane torch from radio shack using a soft solder. I'm trying to avoid the expense and complicated set up of different torches, but wonder if it is possible to solder gold filled wire with butane. I have had no success so far either with paste solder or solder filled wire. I am thinking that I may just have to take the plunge to a better soldering set up. Any advice?

Soldering gold filled wire is tricky because the gold is only on the surface of the metal, unlike the solid silver.  So it is not the butane but the technique that is most important.

 Out  of curiosity, what elements of technique are important here?  Not melting the gold off the surface?

I have never tried to solder gold filled so I won't comment on that but yes you can successfully hard solder silver with a butane torch.  You can choose between soft, medium and hard to build rings and small pendents. The solder you are buying at Radio Shack is not meant for use in jewelry as it is a lead free soft solder. What you want is a silver bearing hard solder that is an alloy of silver and zinc. It comes in three basic grades as I have already mentioned and is in fact silver brazing not soldering. Butane torches are up to this task for small pieces of jewelery.