There are not a lot of "brand name" plug-ins that I think are noticeably better than the open source and/or free plug-ins that emulate them. MAAG EQ-4 is one of them. I tried Luftikus, and another one that I can't remember and Luftikus was the better of the two, but when I finally broke down and bought EQ-4 I relegated Luftikus to the bit bin. Even on (or maybe because of?) my compromised monitoring environment the difference is obvious. I recently tried the UA version, and I think it is ever so slightly different, but on my system I can't pick one over the other, so I'll stick with what I own already - makes for more room in the wallet for libraries<G>!)
Disclaimer - I have used the hardware version, and so I probably favor the emulations because they are probably closer to the hardware. I've also tried building one myself, and I did OK with the Air Band (it's not that tricky really) but the lower two bands eluded me. If I had not become accustomed to the hardware I'm not sure I'd have made this purchase.
Luftikus does an admirable job, but if you really want the MAAG sound I think you owe it to yourself to try the Plugin Alliance or UA versions. If you aren't after the exact sound, but rather like what an air band type filter does than you'll be perfectly happy with Luftikus.
AND, if you are the curious type, the Luftikus source code is available. I really enjoyed looking through it, and now that I'm thinking about it I need to go back and study it further. A very cool bit indeed!