For a simpler inexpensive envelope filter, try the tonefactor (or mojohand as its now called).
I had the Frostwave funk a duck and its an incredible filter, but expensive. Its built real well and needs a wallwart to operate.
I also had the Mooger fooger filter, but its also expensive,large and sucks alot of tone.
ill tell you upfront that a lot of people have a problem with its size, but if real estate isnt an issue for you then id say this might eve be a better choice than a mutron. very similar jerry garcia type tone, and under 200 on ebay. also doubles as a phaser, although it isnt great
Not a bad idea if you're not sure. I've had the mini-Dano and the Ibanez soundtank autowah. Later ran across an old Ibanez AF-201 that costed many times more. The AF-201 is richer, more organic has more quack and many different sounds. Neither unit though could be called "transparent" or true-bypass. After all the effect is a filter, meant to screw up your tone and change your sound a lot. /C