I would recommend getting a good GA headset and worry about a jet compatible headset when you get hired to fly that equipment. If you're a CFI now you know how uncomfortable a traditional DC esque headset can get after a long day. I would recommend either the Bose or Lightspeed Zulu. I recently purchased a Bose earlier this year using their 0% financing ($83 a month/12months). By far the best investment I have made.
I had been a long faithful to my DC's and was planning on getting a telex or something similar when I got to a regional. But after my furlough last year I realized I would be spending a lot more time in pistons. In the interests of preserving my hearing I've invested in the Bose. It should also work out as tax write off as an independent contractor.