EDIT: disregard, found help elsewhere.

I'm trying to buy a memory foam mattress topper (3" and at least 4 lb per cubic foot density), but I don't know who to trust...

I have strongly considered the following, but part of me always wonders if they're flat out lying to me (and the last one actually has a review somewhere saying it's dishonest advertising):
PostureSense 3-inch Thick 4 Pound Density Memory Foam Mattress Topper
Memory Foam Liquidators Memory Foam Mattress Pad - 4 lb density - 3" Twin - Natural - 3"D Twin - T43
SleepAid Factory (HealCo) Dream Memory Foam Toppers

And loosely considered these as well:
SleepWarehouse Premier Plus 4lb 3" Twin Memory Foam Mattress Topper-On Sale+Free Pillow!
All Memory Foam 3" Memory Foam Mattress Topper Full 4lb Density
Healthy Foundations

I know tempurpedic is *the* brand, but surely they have some meaningful competition? What brands can I trust to not be lying to me when they say it's 4 pound per cubic foot density?

EDIT: disregard, found help elsewhere.