I'm looking for inexpensive bookshelf speakers.

Usher S-520, they sounds like ProAc Response series. They do need some muscle, but your Denon receiver should be fine.

Omega Super 3, $550 new. 93db and 8 ohm will work well with the Denon.

If you can find a used pair of Totem Rainmakers, they should be on your "short list" to audition.

depends what type of sound you are looking for. For the money you could do better than the B and W 602. The Acoustic Energy Aelite or discontinued Aesprit provide very open clear sound with rounded off top end and limited bass extension. They clearly benefit from bi-wiring. Can be had on e-bay for under your budget. The Quads are excellent but the finishes are unique (very glossy). The wharfedale is an excellent value. Not familiar with the others.

a used pair of Epos ES-14s would be perfect.