Axminster do the SX4 with R8 taper which is a bit more useful than the MT4 or use a MT4-MT3 reducing sleeve.

J

have you considered the 626 which seems to have some following on here in it's Warco equivalent.

For the same money, you can get good condition old iron. Well worth looking at.

I wouldn't worry about rigidity. Generally, a concern with round columns is position repeatability on the z axis, but there's a key that's meant to see to that. You may well find lack of a knee a nuisance when tool changing, and the high minimum speed a handicap also.

That said, it looks like it's excellent for high speed fine work. so I guess it depends what you're doing. Personally, i'd prefer a knee mill.

There was a thead on another Senior mill here a few weeks ago, which may be worth a look.

The myford and denford 626 and 836 may be worth looking at too. One issue with the 626 and 836 is their provenance. While there are many happy owners, there are also a few horror stories on the net also, often to do with warped castings. Proper stress relieving is an expensive process.