Offers for ebook re-publishing of old titles - what should I do?

Hi,
I published four thrillers in the US during the late 1990s with major houses. I think three of them had reasonable stays on the USA Today bestseller list. After that I had a complete change of creative direction and changed my agent to one in the UK where I live. Now, 20 years on, I've fielded two out-of-the-blue offers to republish my US titles in ebook format from US outfits I've never heard of, namely Crossroad Press and Speaking Volumes. They seem to be "genuine" operations, in that they seem to produce ebooks (and even some print-on-demand), and I think they specialize in republishing back catalogue titles, but I have no idea if these offers would yield actual royalties, or how these operations go about selling their copies. Are these sound propositions or a sort of "warehousing" operation?
I have recovered rights to my four thrillers from the original publishers, so the licenses are mine to bestow once more.
Can you offer advice on this? Any thoughts or information would be much appreciated.
Thanks!

Thank you.

Good advice. Unfortunately I am no longer in touch with the agent I had in the US back then, and the UK agent I have now doesn't have any information. This kind of back-list epub operation doesn't seem to have arrived in the UK yet.

Thank you. That's a good thought. Somehow I don't think my agent is going to prioritize this, but I'll give it a go!