The 718 DMD are quite amazing little speakers, they treble with the new DMD tweeter is detailed yet sweat, they have excellent dynamics and deep bass for the size of the cabinet.
The Spendors are a more traditional English sound, very good performance, with a very nice liquid midrange but are not as transparent, or dynamic as the Ushers.
You can't really go wrong with either speaker both speakers are aroudn 87db or so you would have enough juice to power either. The Usher's will sound marvelous with a tube amplifier as they are a more transparent speaker to begin with.
Dealer disclaimer