I worked at a mattress store a few years ago.
Stay away from sleep number. If you want more details why, let me know.
Waterbeds are still around. They just aren't popular anymore because they're unnecessary with the tech we can put into beds today. They're heavy, expensive, and require care. Next generation is gel.
@OP how long ago did you sleep on a tempur? The first generation sucked hugely. Way too hot. I actually sleep on a tempur cloud supreme and it's really not too bad (I'm a warm sleeper too). I find it extremely comfortable, but everyone's comfort is different (otherwise there would only be one type of mattress to buy, right?)
If you're totally against tempur, mx=headroom nailed it. Go with an individually pocketed coil mattress. They work well for side sleepers because they let you sink in where you need to (hips, shoulders). Simmons is known for their individually pocketed coil.
KEEP IN MIND: Simmons also uses memory foam for the top layer of foam on several of their mattresses. If you think tempur is hot, a Simmons with the memory foam on top will be no different. Try to find one with latex on the top. It tends to be the coolest foam and it conforms similarly to memory foam.