There're better floorstanders than BW 684. But it's a matter of taste. There're many who are keen on BWs.
I would try Epos M16i, QUAD 22L2 or Acoustic Energy Aelite Series. Their sound character are more natural.
By the way, I wouldn't go for NAD 355 or 356 when upgrading the amp. There are better amps in British market for sure like Creek 5350. Creek's amps have great sinergy with Epos loudspeakers as they were designed together. Creek and Epos belong to the same group actually (owned by Michael Creek). Creek's products are designed to last for decades (very solid) and its after-sales service is the best I've ever known. Last time I need a technical support, Michael Creek himself helped me on phone. What's more, once, afterwards it's passed 5 years, he mailed me an brand new manual of the Creek 5250SE integrated amp I owned. Furthermore, I hadn't ordered it, he just mailed it after knowing I had lost it. It's really impressive, as I live abroad! I'll never forget it certainly.