Your set-up should work.
What I have just found frustrating with the 'enclosed bookcase/ enclosed bookshelf' type of placement is that the more expensive speakers don't usually perform much better than more modestly priced speakers.
So, I am not surprised that Harbeths are not mentioned ... you will not get your money's worth.
I had picked up Rega Aras for $300 NOS and they performed well on enclosed shelves. Good bass for their size. I also used Energy RC10s ($350) and they performed well, I decided to do a major upgrade and purchased the Spendor SA1 ($2100) and they sounded mediocre, which surprised me since they are sealed boxes and port issues should not be an issue. Also, the Spendors were designed with shelf placement in mind. I then auditioned Totem Mites ($750) and loved them in the store, but they were just so so on enclosed shelves. It is the enclosed aspect that is the great equalizer.
I came across the Ascend Acoustic Sierras and they have given me the upgrade boost that I was looking for. I had them on shelves and recently have moved them to on top of the bookcases. The sound really opened up when I took them out of the enclosed setting.
Rich