Depth does matter but it really matters more about the manufacturer, but you should be fine with a 10".
The mattresses you listed are okay but I can teach you how to get a better deal.
The prices go like this -200- Cheap bs foam CHEAP -500- A little better foam, probably no harmful chemicals in there glue maybe some gel -1000- definitely some gel memory foam high quality foam should be AT LEAST three quality layers of foam.
Here's the deal man if you go to a mattress store like Sleepys, one of those guys you talking at least, at least 85% mark up on there end and they can drop that "sticker price" 50% if you know what your doing.
In my honest opinion you should spend about $1000 and get a mattress that will last 7-15 years easy. You want something with some type of "gel infused memory foam" and at least a inch of it. Memory foam sleeps "hot" because there is nowhere for the heat from your body to go but up back on you. This will help you more than you know in the long term.
Don't buy online those reviews mean nothing because a person that may be 6'5 and 350 hates it but it may be just right for you.
So here's what you do.
Step one: Have a clear cut budget. Know what you have and are willing to spend.
Step two: Go to a real mattress store. Don't go to a big Lots or Sam's or Walmart any of those bullshit places because you'll actually pay more for shit and be back in two years. Go to a REAL mattress store.
Step three: Be a "One Leg Shopper" and don't buy right away. Make the salesman/women work and be willing to leave and have two or three stores fight each other and drop price, you would be surprised how low they can go, so find something you like that's a little over your budget (400-500$) because you'll save that much easy.
Step four: Say NO. Reject the fuck out of these people and act interested with intention to buy. Don't waste their time but be in control and make them earn your business. You will save more than you ever would imagine.
Any questions pm me but for the love of Pete don't buy online.