I used to sell beds and mattresses. Pls forgive me if I don't address all issues or explain myself fully or cover issues you aren't even asking about. I'll try to address what you're asking. Let me know if I succeed. Also, forgive me if I repeat others comments. My purpose is to answer and provide some general bedding questions others might have and that you might have too. I haven't read much of the thread but I will go back after I post this.
1. you can often use your old headboard (not just resting on it cosmetically) and get it fitted to a metal frame, hooking up the headboard and/or footboard) and supporting the bed above ground. An experienced quality bedding store will help accommodate your need to connect the headboard. There are adapters hardware kits that solve most hookup problems. IKea is not a specialty bedding store. They sell beds and furniture but generally are not much more than clerks - not experienced
'bedding technicians'. Go to a good furntiture or bedding store (not Mattress Discounters, etc.) and tell them your need to connect the headboard to support your whole bed.
Note: Be aware that boxsprings don't do the job properly resting directly on the floor. Some people try to get away with this, though i know you're not. By doing so, you actually shorten the lifetime of a mattress and get less than optimal spinal support. Often times you'll void a mattress mfr warranty if the boxspring is found to be resting on the floor.
2. once you've decided on a high quality mattress, the most important issue should be using and/or purchasing a new boxspring. Due to the physics of support, the boxspring and its ability to provide comfy support (and good spinal health and good rest) requires a boxspring that's well-designed and supports evenly.
3. regarding the issue of bed height, you need to know that in the market there is/are high profile (approx 7-8 in) and low profile (4 in) boxsprings
. Regardless of the bed height, both hi and lo profiles boxsprings support you equally well.
Also be aware that mattresses can and are now generally 12-15 inches thick. They are one-sided, no-flip for the last 8 yrs in North america. This means that the 'bottom' side is not a sleep surface, due to fire safety/protection laws.
BTW, for those that haven't purchased sheets in a while, sheets are now generally all deep-pocketed to fit the higher mattress thicknesses.
General mattress info
4. mattresses have a limited lifetime of support and comfort far less than they are aware of. Most people spend less on mattresses and are expecting more then they should. They keep them far longer than they should.
Based on my experience and industry knowledge, as a general rule if you spend less than $700 on a queen sized mattress, expect it to last less than 7 yrs. Most people keep the mattress & boxpring combo about 12-15 yrs, which is 8 yrs past their effective lifespan.
5. if you can measure a deflection (dip) when you view the mattress bare and measure a dip of greater than 3/4 of an inch away from the plane of being flat, the mattress AND boxspring should be replaced.
What did you say? That's menas that people keep their beds PAST almost twice their comfort lifetime. Most people are also unaware of the reasons why they get poor sleep or have chronic backaches 'til they get rid of their beds and get new and better quality ones. Sorry, but if you spend less than (approx) $700, you'll be back to sore back and poor sleep within a year.
As an example, my personal bedding purchase (limited income) was $1500 for boxspring and mattress. I'm already at the 10-yr-point and it's still flat and supports very well.
I'll post this now and re-edit it if I missed anything.