The bank-merger wave is rolling on. National Penn Bancshares Inc. today announced it would acquire another Pennsylvania bank, KNBT Bancorp Inc. of Bethlehem, Northampton County. The all-stock deal is valued at about $464.6 million and is expected to close in the first quarter of 2008. National Penn is based in Berks County. The company has six offices in Lancaster County and one in York County. National Penn shares are traded on the Nasdaq under the ticker symbol NPBC.