I was on crutchfields website and they have all that you need to swap out a head unit for a 2004 Boxter. My question is, how similar are the 996 and boxter stereos for the same 2004 year?

They dont have any info for the 996, just the boxter, but for the boxter they have the harness and removal tool.

Can the boxter install accessories work for a 996 w/o Bose?

 

Should be the same assuming neither are upgraded bose... Then you have factory amps ect.