Smoke Dog: I have always loved the color scheme on your DF-300.
I have all 3 generations of Blizzards, and they are so much fun...
The DX is the one from the 80's, and are pretty hard to come by. They are well made, real rubber tires on wheels, and metal transmissions in the earlier models (orange wheels), and with dual 380's as well. They also had a version without a plow and a van body called the "Heavy Metal". I don't run my DX much simply because it is nearly impossible to find replacement parts for it.
The EV/DF-300 is the single motor version with the dual disk brake/drag brake steering. These were good quality as well. They need to be completely disassembled when purchased, as they need bearings and other tweaks to run properly. As for the steering, this is what needs the most attention: The gearbox needs to be lubed, and the center diff needs to be gummed up with 120,000 diff oil. The gummed up diff makes the steering go from an "on/off" steering to one with much more feel. One also needs to use the weakest steering servo possible (again, more "feel"), and if you use those AVID fiber-material discs, it makes a huge difference. The stock setup is metal clamping on metal discs, so again, it just grabs and it is an "on/off' steering. These are the cheapest option, and the fastest as well, if you want a speedy cat. You can pull the motor/ESC and battery out of your "summer" basher and use it in this. It takes a while to get the steering sorted, and both sides pulling the same amount, but once it is set, it runs great. This is the best option if you want a fast snow cat. Kyosho also has reused many of these parts on the newer SR, so all the wear and tear parts are still available. Here is a pic of the drag-brake system...
The newest version, the SR, has gone back to the dual motor architecture with plow. I love the dual motors, as it is much more nimble than the single motor version (think fast basher vs a crawler) but it is also not meant for speed. THat is where it ends. This model suffers greatly from Kyosho making a cat with the quality of a child's toy from a dept. store. It has a plastic gearbox with no way to install bearings. The gears are on posts stuck into a plastic plate (not supported on both ends) and that is bolted to a very thin flimsy bottom plate. The motors (370's) are garbage, run so hot under normal use you cannot touch them. THe dual esc's last about 2 or 3 hours before crapping out, but that doesn't matter since they have a double tap reverse and the wires have a diameter of spaghetti and are so stiff, one broke in half in my hand. I have been working hard on making this model usable, and am having good luck so far. Unfortunately, by the time you are done with this cat, you will have many, many hours and many, many dollars spent to make it up to a "hobby grade" level... This is the best option if you cannot track down a vintage DX, and want a nimble workhorse with a plow.
If you want to see my SR struggle, you can look here...
http://www.scale4x4rc.org/forums/showthread.php?t=65501
All the models will require proper belt tension, and the drive chain tension must be spot on as well. You also have to apply silicone, cooking oil spray, or a paste ski wax to the drive sprockets, as well as putting the cat outside for at lease 10 minutes so the parts will accumulate to the temperature (hot tracks / sprockets will have snow stick instantly) to keep snow from building up on them and throwing the track. Although they all need help out of the box, they are so damn fun and different... Hope this helps.