power tools? ive never done a hg swap with power tools.
my best time on a hg swap was just a hair under two hours, from tire off, to tire on. was on a completely stock sohc. dohc typically takes me another half hour or more, depending on how much of a bitch it wants to be on the timing lining up right (and depending on how many bolts are super tight too heh)

on my neon, the 20 min guess is still without power tools. im just so used to taking the thing apart, that i could have all tools out and just get right to work. i have a few things missing or modded too to make getting to some bolts quicker/easier, so that definately helps.
what i find that usually slows me down on a hg swap, is getting that damn stock crank pulley off. sometimes i can get it off in under a minute, sometimes i cant get it off at all. just depends. of course, having the correct puller for it helps a ton, as even a 5ton universal 3-jaw puller can and will bend/break if the pulley is on there tight enough