ditto nothing wrong with mulitable sets i aquired my oo4 because of the price. got it for $750.00 somtimes the deals are on the bigger sets as we all know the 003 is very popular. .5 gph. more than the 003 and the sound is easier on the ear than the 003 to me.
Agreed both the 004 and 005 are noisy but its a much lower tone and its easier on the ears. I can still hear the 005 running from my house and its way over at the barn (400 yds away). The 003 and 002 have more of a cracking noise to them, and they are air cooled which makes them much louder as well.
There are great deals to be had on the bigger sets, my 005 was 600 bucks and runs like a top hard to not pick one up at that price.