What springs should I get
 

It is time to change the tires and do a few minor mods on my 01 QX4.
Currently, the car is stock with age worn tires.
Last 2 years, the truck has been my winter DD but I did use it to take my track bike down to The Ridge and has seen some road trips with 4 adults.

CT has the Duratrac's on sale and with MurdOc's positive reviews on them, they are going to be my new tires. I would like to take the truck on some light off-roading adventures this coming summer so I was thinking of upping the tires from the stock 245/65/17 to a 265/65/17.

Here is where it gets a little tricky.
When I had my bike carrier and bike connected to the rear of the car, the back end sagged a lot.
Actually, even when I have 4 adults in the car, the rear end tends to sag so I was thinking of getting stiffer springs for the front and rear.

What would you guys suggest? I was thinking of some medium springs for the rear and light duty for the front and get a 1/2 inch lift in the process.
Shocks have already been replaced with KYB's.