Help with choosing a Firm mattress from online retailer

My wife and I have never purchased a mattress before, but we recently visited local retailers and found that we like the Serta iComfort Hybrid Recognition Extra Firm mattress. However, we'd like to keep the cost under $1,300 and were wondering if someone could point us to an online mattress retailer that would give us something comparable.

I am 5'10", 200lbs, and usually sleep on my stomach but sometimes my back. My wife is 5'1", 125lbs, and is a side sleeper. Our biggest issue is that I toss and turn like crazy and my wife hates me for it, thus no motion transfer is very important! We also do not like mattresses that have a sinking feeling (memory foam) which is why we really like firmer mattresses. Any help is appreciated!