OOT Sleep Experts: What kind of mattress do you have?

[solids]

I'm not sleeping very well recently. It typically takes me 30 minutes to an hour to finally get to sleep when I go to bed. I toss and turn a lot, and often wake up sporadically during the night. Even worse, I sometimes have a minor ache in my back. The main suspect: my piece of [censored] bed.

This bed was bought from Ikea a few years ago, and features a frame and a $300 mattress. I also put a 2 inch memory foam on top of it, but this basically does nothing. I'm just not that comfortable when I sleep.

I am seriously considering buying a new mattress, but had a few questions...

For all you lucky folk who get at least 8 hours of uninterrupted sleep a night, what type of mattress do you sleep on? Any good suggestions? I'm a noob when it comes to bed-related stuff, but prefer a soft but not too soft mattress.

Can I get a really good mattress for ~$500, or will I have to pay much more? FYI, I only need a mattress, not a frame or box spring or anything. Recently, I stayed in a Heavenly Bed at the Westin and never slept better. Looking online though, I'll have to pay north of $1200 for one of these babies. Is it worth the investment?

Anybody have a Tempurpedic? Once again, expensive as hell, but perhaps worth it? I hear you sweat a lot in these things as well.

This would be a full size bed, btw. Thanks duders.