6.1 addon?

My Receiver is 5.1 ...Can I use a seperate Processor or Receiver with Dolby 3 stereo to get 6.1 accurately?...have any good recommendations without breaking 200.00?...will a sub and an Equilizer hooked to this 6.1 on the rear channels be an advantage also?...I was reading on a way to connect the rear pre-amp outputs from my 5.1 into a receiver or processor with dolby 3 stereo...is this the right way?