
Exped
MegaMat Series
Car camping comfort champ, but some side sleepers find it thin.
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I have dozens of nights on a an older Tensor Insulated (The \~500g one) and I hope I'm not cursing myself here but it's been flawless. I've even used it for several nights in the shelters on Isle Royale with nothing underneath it. Now that I have switched to the Tensor Elite, I plan to unpack my Tyvek ground cloth if I stay in a shelter this fall.
Yeah I have an older Tensor insulated that is 3 inches thick, 4.2 r value, and 20oz, and it also cost around $190 at the time. This Eclipse is just better in every way and doesn't cost more, assuming durability is the same. When my Tensor wears out maybe I'll snag this.
I have an insulated Tensor (previous model) that I love. Also have a couple others that are fine. Setting up in a good spot (the slight slant on my last trip was brutal on my back) helps, and though I'm small, I find the cost/weight of the wide version to be worthwhile.
I would also pick an emo. I have one of the tensors, I think the insulated one so I can use it in snow. It's pretty comfy. I think I found another one of those (or very similar sleeping pad) at the resale section of REI, and ended up having to repair a half inch gas, but some sealant and tape over it, and it's held up fine. So OP, if you want cheap but good, consider if you're willing to repair gear that other people are getting rid of because of repairable damage.
Besides the pad (I have a Nemo), consider putting whatever extra cloth-like material you've got into a stuff sack (I often use the one for the tent, but sometimes just roll things in a fleece) and put it between the knees.
I don’t think anyone else has mentioned this, but if you’re an REI member there are periodic 20% off coupons for full-price items. If you don’t need this right away that might be something to consider. Thermarest also just updated the XTherm and the previous version has been available at a steep discount. I got one for 40% off earlier this month at REI. I think they’re now sold out of them but there’s a chance you could find a deal at another retailer. Have not had a chance to try mine in the field yet but looking forward to it. I have one of the three-season, older versions of the Nemo Tensor and that’s a great pad, too. I also like the Exped Ultra line for backpacking pads.
I have used the Tensor Insulated RW (predecessor of the All Season) and (older generation) X-Lite mummy extensively, and I sleep equally well on both. Therefore, I prefer the X-Lite for it’s lower weight.
I have the NEMO (previous generation) in wide, got on a closeout sale around $90-100 from REI. Works great for me as a 230# side sleeper.

Exped
MegaMat Series
Car camping comfort champ, but some side sleepers find it thin.

Exped
Ultra Series
Lightweight side-sleeper comfort, but a bit pricey and bulky.

NEMO
Tensor Series
Ultralight side-sleeper comfort, but slippery and prone to leaks.

Big Agnes
Rapide SL Insulated Sleeping Pad
Comfortable with side rails, but heavy and warmth claims disputed.

Therm-a-Rest
NeoLoft™ Sleeping Pad
Very comfortable, good service, but heavy and bulky for backpacking.

Ranked #1
Exped - MegaMat Series

Ranked #1
Exped - MegaMat Series

Ranked #1
Exped - MegaMat Series

Ranked #1
Exped - MegaMat Series

Ranked #1
Therm-a-Rest - NeoAir Xtherm Series