I think mattress stores are a scam. High commissions and overhead. We went on line at Costco (Sam's has them too) and purchased a high quality layered foam mattress for around $750. It was delivered free, and with a little help we got it up on the frame, cut the packaging and bing, bam boom we have the most comfortable mattress I have ever slept on. Costco will take it back if you are not completely satisfied too. Just do your research and read the reviews.

I didn't realize they made toppers only 1/2 inch - 1 1/2 inches deep. That probably wouldn't sink like 3 inch deep one I had. Because of the bad back i still needed the support and once I added the topper the support wasn't there and I sunk in too far. Only adding 1 1/2 inch you should still be able to feel the firmness.

Tuft & Needle answers
 

I would say the T&N mattress is around a 7-8 on firmness. Feels very solid, yet I don't sink in too far.

My bed had a solid bottom frame already, so we just put it on that.

You want to get it directly from T&N. T&N is the same price as Amazon, and you only get the 100 day return policy when purchasing directly from T&N. I think Amazon is either 30 or 60 days.

Has anyone purchased a king mattress that is split and inclines for reading etc.?

We just bought our adjustable frame and cool gel extra long mattresses for our king bed frame from mattresses at Marion. The owner is wonderful to work with, saved much $$