In practice, with shelf placement, the use of a front or rear port is not as important as you may think. What will impact the sound more is whether the speakers will be placed on shelves which are enclosed. With enclosed shelves, you will essentially be placing the speaker box inside another box. This type of placement will make all speakers sound pretty much the same, which is just OK. You will lose a lot of the nuances. On open shelves, the speaker sound will not be as closed in and will have a chance to open up.
I can tell you that if your shelves will be enclosed, there are a number of rear ported speakers that are designed with near rear wall placement in mind ... the Rega R1s, for example. The Regas are probably one of the best for this type of application. I was also surprised with how well the Energy RC10's sounded inside an enclosed bookcase. Equally surprising was how poorly the Spendor SA1's and Totem Mites sounded on enclosed shelves.
If the shelves will be open, then the Ascend Acoustic Sierra 1's would work very well. The Sierras can also be placed on their sides with no ill effects. My comments are experienced based as I have owned every speaker that I mention and have lived with speakers on enclosed shelves and on top of bookcases for decades.
My tastes in music run similar to yours ... Americana, folk, country, roots, etc. Try Rosanne Cash's 'The List' or Stills/ Young 'Long May You Run' when/if you audition.
Rich