Sandbags are not necessary and will run counter, as your drivewheels are up front. By adding sand bag in the trunk all you do is increase mass and in certain situations, further instability. If you really want sand in your trunk, I'd use it more for a traction aid to lay down if I were completely stuck.
Blizzaks are king for snow tires in cars.
Other tips?
If you don't have a traction control defeat switch consider installing the kit from ECS. Traction control in low traction situations is great for when you're already moving. But when you're stuck and can't get going, it becomes a hinderence.
Tire pressure is always important in any traction scenario, but more so in low grip situation.
If you have access to vcds you can fiddle around with the electric differential lock, which is really an abs modulated limited slip.
But be careful with this, as too aggressive and it's bad. Too light and you will find yourself "peg-legging" along out of slick spots.
Like someone else already mentioned, these cars when equipped with the right tires will surprise you. Frankly that's any car, I drove a RWD Cadillac when I was in college near lake Erie. Snow tires and the factory LSD got me a lot of looks as I passed by AWD cars that were stuck on a hill.
The biggest factor in low traction driving believe it or not, is you. The driver. Learning certain techniques are helpful, such as recognizing when momentum can be your best friend or worst enemy.
As PDQ said nokians are hard to beat.
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