I just did a search for Thomas Aquinas: http://www.logos.com/products/search?q=thomas+aquinas&Author=Thomas+Aquinas.
Considering that what I was lookhing for was exactly what books by him were included in The Medieval Preaching and Spirituality Collection (34 vols.), I was rather surprised to find that that collection didn't turn up in the search...
And this search is even worse, it doesn't even bring up the individual volumes of Catena Aurea: http://www.logos.com/products/search?Christian+Group=Catholic&Author=Thomas+Aquinas.
You will sell more if people can find the books they're looking for. 
(Btw, why aren't the two Summas split up yet?. It sure can't be an issue with the publisher.
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