I have an 800 and actually have rarely turned the recovery up past 6. I turn it down more than up, but I'm not hunting iron site much. Honestly I don't think you are losing much if your max is setting 6 which is what 3 is supposd to be on the Nox 600. I hunt heavy mordern trash and do pretty good keeping on 6. A 6" coil or a Coiltek 5"x10"might be a cheaper option.
I do like the way you can manipulate the tones on the 800 say in 5 tone that I run mine in almost 100% of the time. That's nice to have.