I've heard some good things about the Lewitt mics, but don't have any experience with them. The 240 and 440 would be good ones to check out. I know that they are widely recommended, but that can change (internet forums can be fickle!). 20 years ago, the Studio Projects mics were the hot ticket, especially the C1.
Of the 4 mics that I mentioned, I have 3 of them, and probably should have bought the AKG as well. I might still grab one, although I really don't need it. I've had the SP-B3s for almost 20 years, and the V67G for almost 10. The Miktek is the last mic that I bought and it sounds very good, with a nice and open sound. I've also got an NT1 that has gotten a lot of use, it's been my preferred vocal mic. If the Signature Series NT1 is the same as the version I have, it a steal at $160! The V67G, although a touch on the noisy side, has a really smooth sound for a mic that cost me $70 new!
I would rather buy a new mic that try to mod something that's lackluster, unless you have equipment to check it, or a REALLY good reference!