I'm looking at DD as a two model series. I'll be out to chase the other 583s, and if I pass a 620 or two then all the better.
If things are looking up on the work front later in the season then I might invest in a 675 kit and a cast iron disc (or twin disc set up), as I think a lot of time can be made up into, and coming out of, corners. The big bore should give similar torque to a 620 for the first few yards out of a corner.
Having said all that, if a bashed-about 620 comes my way between now and May then I'll do my best to find the reddies.
Cheers,
ali