If you plan on keeping the B&K long term that might be a worthwhile investment however, in my experience I had an ST-140 driving Vandersteen 2CE sigs. I sold the ST-140 for 225 and I went to a B&K Ref 4420 which had 225 per channel which I bought for $600. I sold it for a bit more then went to a McCormack DNA-1 for $800 which is 180 into 4 ohms but, drove the Vandy's easier, with better detail, stronger bass, etc... You can pick one up for about $800-900 and the deluxe model is a bit more. McCormack amps can be upgraded to what many consider world class.
Anyway, just another option....