What a lot to think about!
After looking at the Killinger range, the 1500se interests me, the 1450 does seem a little light for such a price, and there are a few reviews talking about it being unstable with larger uneven pieces. As I intend to make some larger items, that is of concern.
There is always a lot to think about, this is part of the problem I think, too much choice.
I turned on the smaller 1400 with out of balance pieces and it was fine. But I hear what you are saying, I don't know many lathes in this lower price bracket that won't wobble if used too high speed for the piece unless you are going to go the the Vicmarc 300, VB or Magma Black Titan range and these are up in the £4000-£6000 + bracket.
Having used all the lathes mentioned here and more (except the Magma and VB) all of them will move if the operator is not treating the piece being turned with the respect it deserves, a powerful 3 phase motor has the power for turning/cut large pieces without the revs, plus large diameter pieces have a much higher peripheral speed at the cutting edge, so again you don't need the revs as with a smaller piece. There is a lot, lot more to a lathe than just its weight.
A large piece of wood flying around at mach three is dangerous and with the power any of the lathes mentioned it is more than enough to cut at a lower safe speed.
I apologies if I am teaching you to suck eggs, but be careful if you turn large out of balance pieces as if a 200kg plus lathe moves/wobbles then it is too fast for the wood being turned ,it is only as safe as the fixing, spigot etc holding the wood. It would be interesting to know what floor these reviewers placed the 1450 on and if it was set up properly, often it is not the machine but the user. Over the years several people in the States have been killed turning large pieces of wood, it doesn't take prisoners if it goes wrong and a full face mask won't stop any such blunt force trauma.
I wish you all the best with your choice, what ever you choose you will have fun with it I am sure and let us know how you get on.