:editor's hat on:
Yes, you really do need to read what they're currently buying or end up writing the wrong thing, wasting your time and theirs.
"Steamy" varies from writer to writer, as does their level of writing skill.
I tried to find sample excerpts on the ordering page and was unable to turn up anything. Perhaps there's something on the writers' websites, but I have no time to look.
One thing that helped me make a choice on which to read were the authors' bios. It was pretty clear they'd written those themselves and little to no editing was done.
A couple I could barely get through; they were simply unreadable. Unfinished or choppy sentences or one long sentence or a packing list of information about the writer (often quite dull stuff) clued me in that I might get more of the same in their story. Now perhaps the HQ editors cleaned up the story, but the raw product of the bios was a bit scary!
I bet I've let myself open to "I write a terrible bio, but my prose is great" posts. Yup, I know that. I just mention checking the bios as a general guide on whether the writer's style might work for me or not.
Also, check to see if the writer has written OTHER things for HQ and if there are samples up on the site or on Amazon.
Yo--HQ, if you're lurking here, put in at least a first page of those stories! If the writer is any good, readers will totally buy the product because the first page should HOOK them solid.