Re: Volume pedal placement/impedance........
EBs are passive, if you go straight from the guitar to the pedal, you want a high impedance. If you have it after buffers or in the effects loop, you want low impedance. If you feed your guitar with passive pickups directly into a low impedance volume pedal, your tone will turn to mud.
As far as where to put it, if you want to use it to clean up your tone, put it at the front of the chain. Vai does this and has his minimum volume set so when the pedal is fully at the heel the sound from his amp is clean (on the high gain channel), when it is fully forward it is his full on tone, I don't think he uses his channel switching much. I like it this way too, it lets you play around with all the in-between tones, do cool volume swells that also have a "dirt" dynamic in them (gets dirtier as it gets louder) and other cool stuff.
The other line of though on volume pedals is to have all of you pedals, especially gain pedals before the volume pedal so you are getting all of your distortion from the pedals, then you can vary the volume of the signal but if doesn't affect the gain (unless you are using your amps gain, in which case the first option is probably better).
Or, if you don't want to change the gain/tone at all, you just want to vary the volume, the best way is to put a low impedance volume pedal in the effects loop.
Hope this helps, it's kind of a personal choice as to what works best for you.
*EDIT* I just read the post you posted while I was posting (try to get the word post in that sentence one more time!). Low Impedance does not = Active, EBs are passive, the low impedance model has a 25K pot and the high impedance model has a 250K pot. Just think of them as the same thing as the volume control on your guitar, except you can work it with your foot, it works the exact same way, it varies how much of the signal is getting diverted to ground. If you have passive pickups, you want at least a 250K pot, with actives 20K - 25K. You can read more at
www.ernieball.com (imagine that).
Actives work differently, don't have time to get into that right now.