Crisp sounding tubes for Modwright 5400ES

I recently upgraded from a Modwright 9100ES to a Modwright 5400ES. While there were improvements, the richer mid-range and more powerful bottom end of the 5400ES tipped my previously balanced sounding system into one sounding a bit overly polite with a lack if crispness in the top end.
Can anyone advise me on what tubes (output & rectifier) and power cables to chose so as to brighten the top-end.
Grateful for your advise.