man, I am so easily persuaded

I'll be picking one up after I move a few things here ....
Really depends on what you're looking for! If you're looking to nail that MuTron tone, it's gonna be the MuTron IV all the way - aside from the TruTron (unobtanium ... at least for realistic $$$) and the OG Mutron, it's my absolute favorite MuTron-like envelope filter. It's a helluva lot of fun as well!
If you're looking for more features and coolness, my second recommendation would be a Meatball type clone - of which the Artisanal Effects Meathead is the current champ. That being said, for pure filter goodness you can't beat the 3 Leaf's that are "based" off the Meatball - namely the Groove Regulator, GR2, and Wonderlove/Wonderlove DLX. The Wonderlove DLX and GR are rarer and more expensive than the Groove Regulator and Wonderlove v1, but worth it. Amazingly enough, the OG Groove regulator and Wonderlove v1 are popping up for "reasonable" prices nowadays - and by reasonable, anywhere from $200-$300 (the DLX seems to go for $500 at a minimum, and I can't remember the last time I saw a GR2 for sale). I think there might be one in the classifieds right now, in fact.
Best of luck!