I'd suggest the little Roth OLi RA1 speakers, which are a bargain at just under £100, and have an excellent sound. For cables I'd buy something simple but effective (ie able to conduct electricity from system to speaker): somwhere like Maplin or a local hi-fi retailer should be able to supply a suitable cable 'off the reel' for around £1-£2 per metre.
I wouldn't bother with speaker plugs: just buy the cables a little too long, make bare wire connections at either end of the cable (ie at the Denon and at the speakers), and if you want to be pernickety about things, cut off the ends of the cable every year or so and strip back to reveal clean metal for the best connection.