There is a new review this month in Stereophile for the 180 discussing this subject. The reviewer seems to love the amps and considers the upgrade from 150 to 180 well worth the cost. Again, it depends on the speakers that you are currently using. Who knows, maybe a re-tube of the 150 will get you where you want to be?
Good luck!
Hoosierdaddy
Good luck!
Hoosierdaddy