they are good players but will add mostly depth to Juve and not raise the level of quality. Plus they are largely unproven outside playing for a lesser team in Serie A. Isla can take over from Licht in the 352 in home games and be an improvement but that's about it ... Asamoah will be nothing more than a back-up to Marchisio/Vidal and even then, the team would lose in threat on offense, as he is a dynamic mid but pretty one-dimensional.
Isla may be able to fill in at a number of positions, but that doesn't mean he is great at it.
Overall, they are good players, who are yet to prove themselves at a higher level but you are not exactly getting them on the cheap.
This being said, had Milan signed them, Milan fans would have also been over the moon but then again, that doesn't mean they would be right.