One thing to keep in mind is your intended application for the plow. If you will be doing residential driveways, a smaller blade will be handier for getting in & around tight areas.
If you're going to be clearing larger lots, then the wider blade is the way to go.
Wheelbase of your truck is another consideration. The wider your turning radius, the more likely you will end up with your rear wheels running in unplowed snow when working around a corner or curved driveway. A wider blade will help reduce this.
Obviously, the $$$ factor has to be taken into account too. Since you already have the plow, I would say use it if it will fit your intended application. If not, look around for a wider one. With the end of winter approaching, you may be able to find some good deals on used plows - just check them over really closely and look for signs of obvious abuse.
I have a 7.5 ft Curtis on my 2000 F250 and think it works pretty well. I only plow residential accounts many of which have cars, obstacles, or Belguim Block lining them which is why I went with the smaller plow. As others have pointed out, it is just about the same size as the wheelbase, so an 8 or 8.5 would get you better coverage and you won't be driving on the snow while you make turns. I needed the smaller width so I went with it. I think the best advise would be to take a good luck at what type of applications you are going to be using the truck for and go from there.
Use the blade you have,and add wings or permanently widen it.I see your close by (I'm in Brampton),so I could show you how it's done,as we have done that to several of our blades,drop by our shop and take a look.I could even do it for you if you wish.
I always read these posts with great interest as to everyones thinking about the plows. Especially the guy that wants to put a 10 foot plow on an F-150 but worries weather or not to get the plow wings tooo!!!! I too think the 8 footers are the way to go and in the market for a used 8 ft meyers. My next plow will be an 8'6 foot fisher vee once I get my next truck.
My biggest issue is bank drive thrus. The eight footers barely make it thru them, dump truck mirrors dont (thats another story)so if you have any of these to deal with that may be a big consideration. I've never used plow wings but if you need bigger that might be the way to go.