Those prices at tirechain.com look pretty good to me! I'd go for the front tires as well - you'll be looking at a bit over $400 before shipping for the whole works.
I pull a Rhino blade behind my L3200. I have a 6', wish it was a 7'. It has swing, rotate and tilt, so you can swing it over and really push the snow over to the side. I built a gauge wheel for it to keep the blade just a bit over the gravel.
I also built a 7' fixed plow for the FEL. I have gauge wheels on it, that allow the blade to stay an inch or two above the gravel.
Pulling the rear blade does a terrific job. Pushing snow straight ahead does quite well. Pushing and steering - the equivalent of an angled plow blade - does not work so well.
The problem is mostly that the geometry of the FEL is all wrong for plowing snow. The push force is transmitted through the FEL arms high up in the center of the tractor. It tries to pick up the front wheels, so you lose your traction in front, but still have plenty in the rear. When you try to steer you have no traction to do it with. If you pick up the plow blade just a bit you put the weight back on the front tires and do much better, but the push force is still trying to lift the front end. It becomes tolerable until you are really pushing hard.
What you are suggesting, using the curl valve to angle the plow blade, will probably not work well at all. The weight of the blade will always be on the ground, never on the front wheels. The push force will always be trying to pick up the front end, so your steering traction goes out the window.
If you keep the curl function or somehow fix the blade vertically to the FEL arms, and add a 3rd valve for angling the plow you will be able to pick the blade just a bit and get the weight on the front wheels, and you should have pretty good traction.