AN2 Driver,
The Stallion is about 10kts faster than the Eagle II, because the Eagle wing mod creates some drag in cruise. The Stallion gains about 300 nm in range over the standard 501, just because of the FJ44's efficiency compared to the JT15. The Eagle's modified wing carries 700 lbs extra fuel, and that's where the 1800 nm range comes from. You have to get to FL410-430 to get that range. At that altitude, 360-380kts, depending on weight and OAT. You can get 400kts out of them in the low 30,000's, but you'll be burning 1100 pph to do it. Not many fly them that low except on shorter trips. Both the Stallion and Eagle II, can go straight to FL430 in about 30 min at MTOW and ISA.