Let's see if I can remember this right... The 6000 is labeled GK (Graphite/Kevlar) and is purplish. Wasn't the 7000 white? I don't remember... The 8000 is labeled Quartz and is red/maroon (all graphite?). The 9000 is labeled DP (Dyneema Plasma) and is green. I swear have seen a 10000 or maybe 12000 in a French store around 1995; it had a leather grip and a rainbow color scheme fading from silverish purple to pink, and it was very expensive. The higher the number, the more expensive, and stiffer/high tech the frame was, it seems. All were shorter than 27 inches, had a wonderful grip shape with a round butt cap, and were around 60 RA. The triangular beam (similar to a Yonex SRD Tour) gave them a muted feel. The inverted bridge seemed almost "welded" onto the shaft, which looked a little clunky, but it was a solid design nevertheless.
As to how they differ in feel from each other... Hard to say... Pretty similar, honestly. My favorite was the 8000 because the sample I had felt more headlight. The 6000 and the 9000 are quite similar, despite the difference in flex (the 6000 is more flexible, around 55, while the 9000 is a little stiffer, around 62 I believe). Both were around 300 grams unstrung with an even balance. I recall the 8000 to have more traditional specs: closer to 12 oz with a headlight balance. Sorry, it's been 25 years...
These are Rossis for the modern age. Although they are stiffer than the F-200 (everything is!), they have that recognizable Rossi feel, with the sweet spot in the same place and that wonderful grip shape. I could not see myself playing with a F-200 in today's game (maybe a F-250), but the Vectris hold their own in today's racquet world.