I think you're making a mistake by buying an amp at this point. The amp you choose needs to work with the speakers it's driving, and since you're looking to upgrade your speakers you'll end up with an amp that works better with your current speakers but that very likely is not optimal for your next pair. I'd wait until you identify your next pair of speakers and then choose an amp that works best with them.
That said, I heard the B60 paired with a Pass Aleph 3 driving a pair of Thiel CS1.5s a long time ago and it sounded fantastic. Case in point, the Aleph 3 may not have enough juice to fully drive your B&Ws to suit your needs, but it may well be fine if your next speakers are more sensitive and/or have a more benign impedance curve.
Best of luck
That said, I heard the B60 paired with a Pass Aleph 3 driving a pair of Thiel CS1.5s a long time ago and it sounded fantastic. Case in point, the Aleph 3 may not have enough juice to fully drive your B&Ws to suit your needs, but it may well be fine if your next speakers are more sensitive and/or have a more benign impedance curve.
Best of luck