Just have to endorse a product here: the ObusForme memory foam mattress topper.
Or probably any memory foam mattress topper for that matter...it is amazing how much more comfortable even our ten-year-old mattress is now. And it feels luxurious while providing good support. I have been having much trouble with insomnia over the past nine months, and now even when I wake up, I'm going back to sleep much easier.
Anyways, they're on sale at Canadian Tire for $140 or so until the end of the week? Jysk also has some memory foam stuff. The Obus Forme one comes with some sort of silver compound mixed in for antibacterial/microbial properties and comes with a very nice hypo-allergenic cover.
We got introduced to memory foam at Sleep Country (which I also highly recommend for great service...ask for Nathan at the McPhillips store) and couldn't afford the whole bed...but even two inches makes a huge difference!
So go out and start sleeping beautifully!