Seriously, on the lower priced end of things, I'd try a Studio Projects C1 into an Audio Buddy or DMP3. If I could have a better pre with some decent gain (much more expensive), then I'd probably try a Shure SM7 on him.
I think Don Henley would sound OK through an NT2, an SM58 or an SM57. Of those you have listed as uprgrades, I think he'd sound different through the C1 than the NT1. I think he'd sound better through the NTK.
When I record another vocalist, I'll think I know what mic works the best and I'll end up going through three or four mics to find something that sounds good. A lot of times I'm right but I still need to go through some different mics b/c the sound I imagined is not what I hear through the monitors but it still ends up being the best sound after checking some alternatives.
You've got some nics mics. I don't think you'd make a bad buy with any of the mics you have listed. I personally don't like the v67 but better people than me do so you have to respect their opinions.
I would use either a U47 or U67 (if it's in your budget). Soundelux makes their own versions of these mics - the E47 (U47) and the U99 (U67), which are quite a bit cheaper/more reliable than the originals. I have an ELUX 251 (Telefunken ELA M251 copy) which is a fantastic mic.
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Post indie electronic
Meriphew www.meriphew.com
To answer more of your question: Woud any of your listed mics be a significant upgrade? No. They'd be different. Better in a couple instances but not significantly better than the NT2.
Meriphew's suggestion, and my original suggestion, would be definite upgrades but perhaps not truly significant.