I dunno much about live sand. I did use some though. I set up my tank as follows: Added aragonite sand (about 30 pounds? I wrote it down somewhere...) and saltwater, hooked up all filters and equipment, ran for a few days. Then I added (this is a 55 gal tank) an off-the-shelf 20lb bag of live sand, I don't think it was specifically arag-alive. I ran this for some time too, maybe a week or so. Then I added my live rock.
This may have been helpful in accelerating cycling, or maybe not...I'm honestly not sure! Live rock does most of the grunt work there, I'm sure, but the sand may have eased the transition a bit too, by getting some bacteria settling into the tank and filtration system early. That's why I suspect someone could even just use some live sand and lava rock and ultimately get the same effects as live rock, though it'd take longer, and not be nearly as cool as critter-encrusted live rock!
THe only prices I've seen in LFS for live rock is very steep, between $6 and $8 a pound, because that includes their shipping cost, their overhead, their profit, and possible curing time. But did someone mention you're in Boston? I've GOTTA think there's a live rock distributor somewhere remotely near you. Perhaps there's a local aquarium you could ask, or maybe try ReefCentral--there's a good chance you could find some regional live rock info there, since they're all about reefs.
Heh. Listen to me...the newbie offering advice...well, take that advice with a 50-pound bucket of Instant Ocean 'cause I'm no expert!
:P
rusty