That was my next thought but the Mrs says no to the Sequoia because it is too large. Looks like modding ours is the least intrusive option. That means adding shocks/struts, springs, remote start, adding a locker/lsd in the rear, and upgrading the sound system. The biggest complaint I have is that it rides like my overloaded and undersprung work truck. Going through our snow storage areas, alleys, or forest service roads is bloody murder because it will rock back and forth enough to almost throw you in the other seat.
Some thoughts on your observations:
1. I put in OEM Audio+ speakers in my 4Runner. Much better sound, crisper highs and better lows. They are plug and play meaning no wire cutting, tapping or adapters needed.
2. Every year I do the Jeep trails in Western Colorado (Alpine Loop and other nearby trails) which are some of the most rugged roads in the country. I have never needed a locker, but do occasionally use the ATRAC button. As long as you go slow and enjoy the scenery, you will probably never need a locker.
3. Yes, the 4Runner has a soft suspension, but after owning two Jeeps with their really hard, abusive suspension, I much prefer the 4Runner. It rides like a cloud over extreme trails compared to the Jeeps. The Jeeps were right down harsh.
If you really plan on doing any off roading, a couple suggestions of things you haven't mentioned:
1. Skid plates: I got the TRD front skid right off. Glad I did for I put a big ding in it on the Colorado trails (tore off one of the red letters). Have not had other major problems but for added insurance I put on the RCI integrated skid plates this last winter; looking forward to how they do this summer.
2. Tires: The OEM tires leave a lot to be desired. There are so many good options out there. I got the BFG KO2 in E load range (those sharp granite rocks in Colorado are something else!) If you are doing trails near Moab, where the rocks are rounded sandstone, you could get by with C load rated tires.
3. Suspension lift: You can do that with shocks and spring sets, or just spacers. A modest lift may be all you need. I have the Rough Country leveling kit which gave me about 3" front and 1" rear. That really is all I have needed.
Finally, I really wanted the TRD Off Road 4Runner when I was in the market, but my son talked me into getting the SR5 with third row seats; glad I did because the grandkids love the back seat (the third row seats are nor really suitable for adults).
So enjoy your ride and have fun.