Hi All...I'm a mattress salesperson and will gladly share what I know.. Please read my advice on five major bedding manufacturers.  I have a Very good customer service rating with my present employer and most importantly I very much enjoy my job..    
  
ok..here we go>>    
  
I.  Serta:  I would most recommend the Serta Perfect Sleeper and/or Perfect Night Lines.  For the most part, Serta offers the most resilient Continuous Wire coil system and places 33% more coils in the middle for enhanced support.  Most of this year's models incorporate a 5 inch dovetailed solid foam border which wraps around the coil system.  This has 2 benefits: First, you won't have to contend with sags occurring around the sides of the bed and this INCREASES your sleep space about 20%. Serta offers many different price ranges and comfort types throughout the Perfect Sleeper Line.   Serta Perfect Night is wonderful but more costly and offers very few benefits over and above the standard Perfect Sleeper Line.  Most Sertas offer a 10 year full replacement warranty against defects.    
  
II. K/K:   **Most of the Coil Systems made by them offer an adequate level of support at the torso area and usually run about $200 less than the beginning models in the Serta Perfect Sleeper Line.  This company is over 100 years old and offers an all around good mattress for the money.  They offer a foam encasement..not as substantial as Serta but it gets the job done nontheless. Their coil system is not as resilient as Serta.  mattress uses a thinner gauge steel combined with a more open network of coils.  mattress has earned the Good Housekeeping Seal in lieu of advertising..so they're able to offer a good solid product with a 10 year full replacement warranty in most cases.    
  
III. Sealy:  Personally, I feel that the Posturepedic Line is costly for what it offers.  There is no foam encasement,  just a styrofoam enhanced edge, and the coil system is not as resilient as the Serta or mattress Brands.  
  
IV. Latex: Expensive but NO Coil system is offers the support and resiliency of latex mattresses.  Look at Latex mattresses with high resiliency foam components to cut costs while gaining other benefits.  Latex usually offers a 15 year full replacement warranty.
  
V. Simmons:  If you and your partner suffer from motion disturbance..ask the salesperson to show you some World Class or Excepcionale Models.  These lines offer individually encased coils so that each side of the mattress operates independently of the other.    
  
**If you're a side sleeper, please look for  plush or pillow top mattresses.  Stomach sleepers should stay with a cushion firm or firm comfort level.  Keep in mind that within each brand, the support systems are identical.  The only variations are pillowtop/plush/firm tops.  All comforts offer the same coil components and support. **    
  
I hope this helps!  Please feel free to email your questions..and I will do my best to answer you..