I don’t understand the comment about needing to bore out the quill, TRBs are typically wider than ACBs for the same ID, so you shouldn’t need to bore anything. Since tapered roller bearings are wider than angular contact bearings, you might need to make a spacer for the outer rings to use the ACBs. The spacer needs to be parallel to within 0.0001”, otherwise your tight tolerance bearings will perform like cheap industrial bearings. By changing to ACBs, you will be reducing the load capacity since TRBs can handle a larger load for the same size, and also will be more rigid. You can get precision TRBs, so unless you plan on running at higher speeds than a TRB can handle, I don’t see the reason to change.
There are a number of varieties of angular contact bearings (ACB), with different contact angles, cage materials, tolerance classes, preload grinds, etc. Which ones to get will depend on how they will be used.
The $50 bearings are probably an industrial grade, the $150 might be a tighter tolerance bearing, but could also be a different variation that costs more such as a universal grind, can’t tell without the full part number. For spindle bearings, $400+ each would be a typical price in the smaller sizes and would be either P4, or ABEC 7 and a 15 degree contact angle. Which ones you need will depend on what is in there, and what will fit with the least modifications. What is the TRB full part number? It should be on the bearing, or you can measure it and get at least the ID and OD you will need for the ACB if you decide to go through with that change.
SKF, FAG, NSK, Timken are all interchangeable. All are quality bearings and you won’t see any difference in performance for identical bearings. Their part numbers will be different, so you will need to reference the bearing catalog for each manufacturer when selecting what you need.