^ Get another topper off overstocked.com and make sure to put a cover over it. DH and I have unfortunately spilled drinks and soup in bed (I can't always get out of bed to eat) and that's kept our topper from being ruined. Anyone who's a klutz, owns pets, or has allergies/asthma should use a cover anyways.
In general though, those toppers help but you need a good bed under them.
I don't know about 10" mattresses but I was sitting on some that had to have been a foot thick or more the other day - with pillow tops though.
Go to a furniture store and ask, take a tape measure in case they don't know and don't mind you measuring the beds.