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

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I have the xtherm nxt and would recommend it. It has a good r value especially considering it's size and weight. The nemo tensor seems to be recommended a lot too in the ultralight space.
NeoAir® XTherm™ NXT Sleeping Pad is what I use and love it as a cold side-sleeper. Love how small it packs down, isn’t too much of a pain to blow up. I don’t find it noisy in the way other pads can be. I know it’s not foam, but I really love it.
You also might want to look at some brands like 3ful and naturhike. They make really good gear for a very low price. The idea is to avoid spending loads of cash on stuff you read a review about and might not need or like. For example the Thermarest Xtherm nxt is an awesome pad but probably overkill for 3 season backpacking, you might be better off with the good old classic inexpensive but indestructible CCF foam pad. The tents you linked have an inner-first pitch, which is actually a big issue when the weather doesn't cooperate when you set up camp for example. Read the wiki, don't spend too much on gear as your first go and build from there.
How much a you inflating the X-therm? The X-therm is only comfortable for side sleepers if you under-inflate it. I recommend playing around with the inflation levels of the X-therm before buying a new pad.
I found the X-therm uncomfortable until I learned to under-inflate it. Have you experimented with different levels of inflation?
We started withe Rapide for our 2P false bottom bag, and later got the Expedition 3R for warmer nights. The Expedition is almost exactly the form factor of our bag. Both are comfortable.
For winter hiking I replaced my Xtherm wide mummy by an Exped ultra 7R regular sized downmat (square model) for a 90 gram weight penalty. Used it untill now til -8C (on wet frozen forest soil and snow). A big improvement in terms of comfort. Also warmer, to my surprise. A possible explanation is that the Xtherm RW version was just too big for me, too much uncovered surface. I have no problems with the down distribution like some reviews mention for the mummy version.
I went from the Xtherm (MW mummy) to the Exped ultra 7 down mat (M) which was a huge increase in comfort. No more soreness, backpain, strain on the hip, or sleeping arms. I can sleep through the night now, instead of waking up several times. Just bought the Exped ultra 6.5 for 3 season use and it feels same comfortable. Tried the Rapide in the shop, definitely also comfortable, but you can find everywhere reviews that it runs cold.

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