Looking for some suggestions on a mattress to help with back tension.

I currently have a Serta mattress which was bought in 2009 for $1200. Although it has held up well, the past year or so has been painful. I might get laughed at in here, but I hadn’t really considered that the 16 year old mattress might be the cause of finding myself waking up tense.

I read the FAQ, but would like some suggestions. I like a firm queen mattress and my budget is around $3k.