Go for x5k. Yeah, not so cheap , but there is pluses of x5k:
2). have no problems with FPU.
3). put any kind of cards you want
4). it is already here, in sold, have working os, kind of tested.
And there is why i don't go for Tabor if i were any new user:
1). slow in compare with x5k : browsers will not be _that_ fast. Youtube, movies, modern games : all will be not that funny.
2). fpu problem. Yes, there is emulator will be. But it also will be not 100% uber-cool, there for sure will be issues, and glitches with, which need to be fixed. Some things may even never work over emulation, so you will have some hard times with some software imho.
3). its not here. when : no one know. It should be in 2015, now its about 2019. My bet : 2021 MAYBE.
4). it is known, there is no audio driver at the moment. I do not know what the problems, but there is none, and when/if no one know. There is also problem : if no onboard sound, then 1 single slot gotten by GFX card, and as result no audio. So only be in hope that there will be onboard audio driver (if and when).
5). i do not know , but i feel something wrong with Tabor. I read everywhere that aeon says "hardware is ready we wait for hyperion", and from hyperion "os is ready, hardware is not ready". So i kind of feel there is some issues we know nothing about.
All of this mean : go for x5k.
And even if tabor be there right now, i still says go for x5k. It is faster and well tested already. If your hope its not only play with workbench, but trying to do something more modern , then x5k only.
Besides, emulation of old classic amiga on x5k much better just because of good cpu. Take a look at my video about classic emulation on x5k: https://www.youtube.com/watch?v=PAGlC9uo644
Someone also saying there something about "multi core". But that probabaly will never see "real support" as we can hope of it , because of many factors, but x5k with even 1 single core 2.1ghz cpu are good for everything (well, for most).