I think that the Roland keyboard amp/PA is pretty versatile.
First of all, sound is subjective. My personal experiences with the Roland KC300 are pretty bad. It really misbehaves itself in live rooms and they aren't suited to display acoustic instruments accurately.
I'm afraid most cheaper PA's are more suited to play electronic music than amplifying acoustic instruments.
The typical answer here is: get two mackie srm450 active speakers and a mackie 1200 mixer; that's about your budget (2200Euro) and judging from comments on the forums, it is also pretty decent in sound quality.
Standard questions: how loud do you want it? Maximum weight? How much low end?
German brand AER is one of the best in acoustic amplification and it is lightweight stuff, but also very expensive. For example: AER CX8 active top + AER Sub10 passive sub + Mackie 1200 mixer = 1800Euro; but this is mono and won't go near as loud as the srm450. But it will sound good.
You might check out the Crest line of powered speakers. Unfortunately I don't have any experience with them. They may be worth a little investigation though cause the amp is built in and they sure have a lot of years bulding top notch power amps. Maybe they would bring the same excellence to everything they are working on (but you'd have to find out for yourself).
In general I've always been quite dissapointed with keyboard amplifiers.
In answer to your questions, I'm looking to bring my piano up to the sort of volume that is balanced with a drummer playing with light sticks (which can be quite loud) and project the sound further into the room. I'm not bothered about weight or size, but I would imagine that pole-mounted speakers would be better as floor mounted would lose so much of the sound if people are standing up. I also wonder if 3-way would handle piano better than 2-way. Finally, I already have a mixer, so it's just the powered speakers that I'm looking for (up to £2k)