CCN Matthews is fairly large and general, there may be a PR specialist specific to your industry that would be able to do things in a more targeted fashion. You might also want to take a look at prnewswire.com.
I send out press releases to audio magazines (i work for an audio design company) regularily and they usually just run them at random. My best advice would be to get in good with editors of publications that focus on your industry
Newswire is what we used years ago, I think I'll go with that. I work in a market research company and want to send a release with results for a study we're doing now so newspapers can pick it up. I don't know if anyone remembers but there was a thread on tribe months back about personal freedoms right after the London bombings like cameras in public places, losing civil liberties, etc. That was mine too. This isn't quite as shocking as that one but it's in the same vein.
Check out PR Newswire. The trick is to sign up for the smallest physical distribution you can. They always throw in Internet and wire distribution for free... and with the RSS syndicated world we live in that's more than enough.