I have a pair of Wharfdale Diamond 10.7 speakers hooked up to a much older NAD amp (7175PE) in a similar sized room (15x40, with 8.5ft ceilings) and I love them. Great detail and great bass. They are now the older model and available for less than your budget from Music Direct.
https://www.musicdirect.com/speakers/wharfedale-diamond-107-tower-speakers-pr
https://www.musicdirect.com/speakers/wharfedale-diamond-107-tower-speakers-pr