I have both, they are both mark 1's.

The 5500 suffered from too much bass until I replaced the tweeters and it was a whole new ball game, they are so much more balanced and detailed now. I have them in a small room that before the tweeter switch they overwhelmed the room, but now they sound great.

The 5000's didn't compare to the 5500's even before the tweeter change, I'm thinking the 5000's will benefit from a tweeters change also (see the tweeter thread regarding the ferrofluid filled tweeter).

1. 568.2mm & 3xDSP5500 2. 565/562 & DSP5000's 3. Director & 568.1 & Edge Amp & Klipschorns