Check out Larry Greenhill's review in the Sept. 99 Vol. 22 No. 9 Stereophile where he reviews the 334. He specifically talks about how the 331.5 relative to the 334 and 331. BTW, I am a very satified owner of a 331 as well. Good luck...
Levinson 331 upgrade to 331.5
I bought the 331 used and the list price for the .5 upgrade is $1,900. It seems rather pricey when I considered what I paid for the 331. Love the amp as it is, but would consider the upgrade if it could really take it to a level that justifies the cost. If anyone has been in my shoes and done the upgrade I am very interested in their thoughts and opinions. Thanks much.