IMHO floorstanders just don't have the same coherency, lack of box colouration and timing as standmounts. It would be a real minefield switching, especially due to the initial impressiveness that 'bass weight' can impart - in the mids though it isn't the same, standmounts rule here.
Or, Royd Minstrels and Rega Ela 1.5.
Having spent a fair bit of time with Epos 11 and 14s, i'd say that the midrange on both is particularly good, and you'll struggle to find something as good which doesn't have a dedicated midrange driver. I'd also say that the tweeters in the Epos speakers is the weak spot, and more modern designs definitely can improve on this aspect of the Epos speakers.
So, I think you are looking for a small floor standing speaker of 3 way design, with a modern expensive tweeter, all for £1500... Hmm...
If I were you, i'd probably investigate what PMC/ATC offer even if it's above your budget, and by comparison decide whether you are going to get something that seriously out-performs your current setup. It wouldn't surprise me if you find something better, but decide that it's much more than you want to spend.
If you find the ES14's dull then something was wrong.
It's common to blame the tweeter and it's true that it's easily excited by ragged sounding sources. However, I would say the real weakness is the way the mid/bass transfers to the tweeter; as the mid/bass is run completely open it relies entirely on the mechanical properties of the cone. I think a lot of the rough quality the tweeter is often blamed for is actually the sound of the mid/bass driver breaking up at the top of its frequency range (this occurs well into the range that is usually considered to be the treble domain). This issue is pretty much endemic to all speakers that use very minimalist, or no, crossover.