In the Quebec market, a 6 year old sled will almost always have really high mileage, Ontario is a little better but you will pay for it. I think about your situation quite a bit as I recently purchased a 2014 Viper LTX DX with 13000km (~8000 miles) for $5700. It came with a brand new track, new trihub, and a new center shock. Once you decide on the model you need to think about reliability, cost of ownership, and resale. Without a doubt if you're not comfortable doing your own wrenching, it will be cheaper to own a newer machine. Keep in mind you will probably want a different sled in 3-4 years and will need to sell this Viper.
Based on Ontario/Quebec kijiji pricing.
When you go to sell it you will likely get ~3000. If you have to put about 1000 in parts (carbides, battery, springs, shock rebuilds etc), it will cost you about $4000 (3000 residual +1000 parts) to ride this viper for 4 years . A 2014 viper with lower mileage sells for around $7500, and it will likely need less in repairs, after 4 years may be worth 4500? So the total cost of owner ship is 3000 over the 4 years (actually ends up being cheaper). This math gets a little tighter when you consider you will only be paying the 15% PQ sales tax on the balance of your trade in for the high mileage Viper ( tax on $2500 vs a $7500 sled).
In the end, if your the type of owner that likes to tweak you sleds (trying different ski/carbides, clutch kits, ecu tuning, progressive springs, 4 wheel kits etc etc) non of this math matters... It will expensive lol.