Mattress Forum

I'm a firm sleeper and like the feel of memory foam.  After trying out several beds and researching, I narrowed it to the Simmons Nethanial Firm "Advantage Collection" (Slumberland's branding of what I think from researching is the NXG 100F) for $1300 and the Tempurpedic Rhapsody which was $3150 (with foundation, queen comfort pillow, bed/pillow protectors, and frame).  Since this is a long term purchase, I did not mind the significant investment to get the right mattress.  However, now I'm in a quandry.  First it slept a little hot so I changed the sheets, which solved that problem.  Now it feels "solid" and I wake up 4-5 times a night to shift.  However, no pain and it is comfortable.  

I went back to Slumberland to purchase some other things (two weeks after my purchase) and I noticed that they had a "reselect" (someone tried it in-home w/ cover protector and didn't like it so they traded, so basically new) of the Nethanial for $700 with foundation during their clearance sale!  Not to say I'm having buyer's remorse, but can anyone advise me on which bed will be better for the long term?  A $2,400 difference is a big chunk of change. 

I have a 60-day return policy for a one-time trade (less return shipping & charge for the free stuff included) so I would like to continue to sleep on the Rhapsody to see if it will "break in" and if I will adjust to its different sleep surface, but if someone buys that Nethanial before I decide, then it's gone --  the clock is ticking. 

Does anyone have any insight on the Simmons NXG firms (or Slumberland's equivalent) for the long run?  Its supposed to have heavier gauged coils so i would imagine it would last 10+ years before sagging.  $600 off is a tremendous deal, but if it gets uncomfortable over time due to sag or break down then it doesn't matter.  There have been few reviews online and the ones I found are favorable to mixed.  Any advice on the Tempurpedic Rhapsody? Durability of the foams compared to the Simmons inserts?  Longevity is the key deciding factor next to comfort for an investment this large.