Just bought a Serta Extra-Firm St. Charles from Macy's and the first two nights have been murder on my hips, shoulders and arms, almost like sleeping on a board, although I have no pad whatsoever on it as of now, just mattress. I was just about to go back and exchange it for something a little softer but decided to read up a bit.... [AFTER purchasing, duh]

I'm a 6' 1, 260 lb. side sleeper and I think I may have bought the wrong firmness for a side sleeper like me.  It was Macy's last day of their 'closeout sale' and my 25 year old Sealy [yes, 25]  was beyond shot so I foolishly impulse-bought the extra-firm Serta.  I obviously didn't do my homework which is unlike me when making a puchase.

About 90% of Macy's mattresses were pillowtops/memory-foam tops and I just wanted a regular firm mattress, but I may have overcompensated for my saggy old Sealy by buying the extra-firm Serta, as I don't really like to sink in too deep to a mattress and am concerned about developing sag spots. 

Since I already purchased, I'm now stuck w/Macy's poor selection of non-pillowtops, though I do have 30 days to exchange it @ a 10% loss plus $70 delivery/exchange fee. 

Macy's only stocks a couple firm non-pillowtop/non-memory foam models by Sealy, Serta and Simmons. My initial thought at this point was to just exchange the extra-firm and buy a regular firm non-pillowtop Serta or Sealy.  Or should I just keep the extra-firm Serta and add a topper as recommended in this forum?

here's a link to the model I purchased...the other Serta St Charles model they offer is a cushion firm, which was a little soft for me.   

http://www1.macys.com/catalog/product/index.ognc?ID=368949&CategoryID=25961

I realize everyone is different and trying out a mattress is the only true way to find what is best for me, but does anyone see anything else from Macy's selection that might be a good solution, or just go w/a topper to soften up what I already have?

And is one brand from the big 3 'S' manufacturers typically better than the other as far as durability, or are Sertas, Sealys and Simmons all poor in the durability dept? I tried to search online but found very conflicting opinions.

p.s.  I didn't really like the Tempurpedic.....thanks in advance