I can't say how much of an improvement the cooling system upgrade was. The truck needed a water pump when I got it, so I put the HO pump on it right after I bought the truck and before I towed with it. I can say that, with the HO pump, it did great as far as towing temps go. My guage in the dash would stay right around 200 - 215 ish all the time anyway, even without towing. Clean radiator, new thermostat, HO water pump, fan clutch working properly, 9 blade fan, etc. I used my infared thermometer a few times on the water crossover, thermostat housing, radiator, etc and it always showed 190-197 even when the guage showed more. I guess the guage was just a little off. Search around on the forums a little about the fan. I found a factory 9 blade fan on e-bay and put it on my 95. A lot of guys have the part number for a plastic fan for a duramax that supposedly fits right on your fan clutch and moves a lot more air than the factory 6.5 fan does.
The max-torque chip made a world of difference over the stock chip. It really was like driving a totally different truck. You read that a lot when people talk about chips for a 6.5, it's true in my experience. The chip was the 2nd mod that I did to the 95. I straight piped the factory exhaust and then put the chip in. I got the max-torque chip pretty cheap off a fellow member who had totaled his truck, and I just to see how much of a difference the aftermarket chip would actually make. Everything about the way it drove improved.... get up and go, towing power, drivability, no more check engine light for overboost (I had a home made turbomaster on it), so on and so on. I definately recommend some type of chip as a big improvement for your truck.
If I were going to buy another chip, which I will at some point for the suburban, I will buy the "KOJO" chip because it's custom made for your mods and for what you use the truck for, towing, normal driving, plowing, etc. I am not advertising for him or anything, I just mentioned him because he is the only person that I am aware of that custom burns chips for 6.5's. There are several other vendors out there that have chips for 6.5's, but they aren't burnt based on the mods you have done to your particular truck or based on what you intend to do with your truck.... more of a "one size fits all" kinda chip.