I'm from Australia so I can't help with suggestions but I have worked in Automotive for a while now and suggest possible doing it yourself as all you need really is a circuit tester, a soldering iron (or electrical tape/connectors if you can't solder) and a normal AA battery to test the speakers... Its a4 pretty easy job.
Try Executive location on Hillcroft. Good customer service and they do a good job. http://www.xmhouston.com/