The Titan Fenrir does have a backplate yes and so will require removing the mobo to fit, not sure about the Akasa. TBH any decent cooler which will be any good for OC'ing an i7 will require a back plate to ensure a proper fit and also due to the weight of these things! They are all similarly easy to fit once the mobo has been removed!
edit: check around for dimensions etc as some people have had probs with some of these big aftermarket coolers if their cases aren't big enough! Again, to OC an i7 you will want a decent case with good airflow.