I agree with HyFlyer. I've operated both Legacy (600&650) and Challengers, the Legacy has a much bigger baggage bay, carries more and as an adapted airliner is more reliable. It won't quite manage the same range as a Challenger and it's a little slower but still the better option I reckon.
A range requirement of 2,000 to 4,000Nm is rather strange; 2,000 is not very far but 4,000 is a heck of a long way. Where do you plan to operate? What city pairs??
3 Point
BTW, 1700 hours a year is three to four times what most bizjets are doing, are you sure? How many crews will you be hiring??