Just looking round and researching everything at the moment here, and thought I'd add my experience with the brake conversion I did on my Subaru Legacy Wagon as it displays a relevant point.
I went from a twin pot, 314mm front to a 4-pot 328mm setup
And then a single pot 298mm to twin pot 314mm rear setup
The relevance of this was that the front brake upgrade alone did very little.
It shifted the bias toward the rear of the car, as proportionally I was now pushing more fluid in the front relative to the rear, and thereby altering the ratio at which the forces were applied.
This was in part balanced by the increased swept are on the disc and the larger pads, but provided no significant improvement in feel or power.
Upon swapping the rears however, this balance was restored, and the front brakes perform as intended. The pedal was very firm, and the feel and power approximately 50% better than stock, and the car stops on a sixpence.
If you're looking to swap the fronts, I'd suggest swapping all four corners from a set that are designed to work together. The difference is like night and day compared to a front swap alone.