So back to to the spindle then about the best value for money IMO is the Chinese WC spindles, the smaller 1.5Kw would do nicely on a little machine and take cutters upto 7mm.
They have relatively low run out and high duty cycle so can run continuously unlike most cheap air cooled spindles that often have Low duty cycles so will need to be turned off and rested after just an hour or so's continuous running.!! . . . To get anything to even compete you'll be spending lot more money.!!