The original 2 series speaker was not time aligned and the DQ10 probably did sound better but all of that has changed. The DQ10 made an attempt at time alignment by the way the drivers were mounted(even though it wasn't) and also used a minimum baffle around the drivers that accounted for some the air the speaker exibited. Everyone was after a duplicate sound of the original Quad(a beautiful sounding speaker but you had to keep replacement panels handy) then.
I always found the pair I had to be on the bright end of the scale.
The DQ10 has been way surpassed by the later Vandersteen 2 series. Modern measurements have allowed this along with better drivers and electrical parts. As Sean says, you could probably mod the hell out of the DQ10 and it would be ok if the drivers could hold up their end of the bargain. The Advent woofer, I thought, always sounded better in the Advent speaker. I know the surrounds were a big problem as with most of the Kloss foam surround drivers.
The DQ10 had a big sound driven by Dynaco electronics I used at the time. It was just too bright for my tastes and I moved away from it after about a year(of course I wish I knew then what I know now about setup, etc)