Quadro fx1700 vs ATI v5600

Who says they favour the FX1700? They may not know anything differently. I guide the purchases in mine and a few other areas, and if it weren't for someone like me, many people would simply buy something similar to what they had last time, or whatever DELL, HP or IBM sent them for the price.

The V5600 is pretty consistently better overall, but it does depend on what you're intending to do with them (apps, settings, etc) since there are some apps that favour one or the other.
Although I'd recommend the V5700 instead of the V5600 at this point, significantly better.

Yeah Hothardware's reviews are pretty good (they include some tests other areas don't). I prefer 3Dproffessor, but their reviews don't always do head to head, so you get a good feel for tech etc, but not necessarily how they match up unless in a specific test.

As for Dell limiting your choices, I know, we order from them here too, and sometimes you have to go outside the box for the best fit for your solution. The nice thing is usually it's cheaper that way.

IMHO the reason being that the V5700 is pretty new, so it might be they haven't added it yet, and removed the V5600 in anticipation of the new product (and avoid complaints). Of course they could also just be targeting those that offer them the best return.