Lets do it again

Thanks for all the info fellas... well its been two years since I asked for your opinions and I had decided to go with the T600. I am so glad I did. With its Cummins N14, 13 Speed Transmission, 3.55 rears, I consistently average 7+ MPG, at 60-65 mph, 1300-1400 rpm. This truck with this motor hasn't given me any problems. Hasn't been in the shop once. It has 1.2 million miles, and runs great. However it is developing a oil leak, which I need to address. But the interior is very quiet, the VIT package is very nice, it has 18 guages, day light doors, sunroof, one piece windshield, easy reach dash, electric windows, heated and power mirrors, smart wheel, dual spot lights, 72" Aero-cab sleeper and a full fairing kit. And I only paid $13500 for it. However, now I would like a W900L with a studio sleeper, with the same or similar specs. I've found an 03' with a ISX (non-EGR). My question is, what kind of performance should I expect from this truck? It has a 13spd, with 3.58 rears... I just love those W900's...