The Brother High Torque spindles are excellent. It has about 3 times the torque as a standard spindle. I set one up to tap 3/4 NPT and it handles it like butter. Die cast aluminum but still impressive. Also we run a 1.6" drill in steel and tap 1"-8 in steel no sweat. Still runs on a 30 Amp breaker (10.4 KVA). It will run 10k all day. Accelerates 0 to 10k in .1 seconds. 10k forward to 10k reverse in .2 seconds. High Torque has 15mm larger bearings than 16k. Steel bearings versus ceramic. Very rugged. Drawbar force is about 200 lbs higher, Big Plus is standard. Coupling between motor and spindle is massive too to handle the torque. I have several clients that have replaced all of their 40 taper machines after trying out the High Torque. That being said it is not a 40 taper. We still recommend running 5/8 and under end mills as short as possible and hsm or hem toolpaths. A big step up from the standard torque BT30 machines though for larger tools, heavier cuts and longer stickouts. If you run end mills primarily under 3/8 and very short (under 1") axial depth of cut the 16k may be a better fit. The extra rpm will help with smaller tools and chamfering/engraving.
Here is a High Torque machining steel. The 'laughing(roughing)' end mill and the slitting saw made my heart skip a beat.
[brother] Machining example of SPEEDIO "F600X1".(Steel) - YouTube