Bookshelves or floorstanders? With the lack of any indicated budget, I am going to perilously presume, that you are perhaps looking for speakers in a similar price range as your amp - if so:
For bookshelves - I guess Q acoustics - 3030i is on deal at hifimart, maybe Concept 20s as you are going to put in a sub, they are impeccable with a sub. Elac debuts go with the 5.2 as I found them more composed and the Sub would help cover the smaller low end and maybe Monitor Audio 100, never heard them, but their reviews are generally very good - they might be a little too bright with the Denon; but I can only speculate.
If you are looking at floorstanders - I have no suggestions in that price range, but if you can give a budget, I can perhaps pitch in with more options.
Also please note - I haven't heard this amp at all, but I have gone thru a couple of Denon amps in the past and I am just basing my match-making suggestion on that sound signature. Audiophiliac gave this amp a pretty big thumbs up, talking about the performance to price is hard to beat if not impossible.
