Amp's that are better sounding than a nad 3020

Take a look at the Yamaha A-S301 and the Cambridge Audio AXA25.  Not a lot of choices at your target budget.

Each amp has it’s " qualities ", attracting various listeners. What speakers are you listening through ? What is / are your sources ? What music do you listen to / enjoy ? How loud do / would you listen ? Do you listen at a distance, or nearfield ? BTW, I am assuming you are talking about the original 3020, or the later 3020a. Have you ever heard a completely rebuilt and upgraded 3020 ?, as the circuits were brilliant for that time.

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have two sets of bookshelf speakers 

one is 4 ohms 90 dBSL AND OTHER 

6 ohms at 87dBSPL for a 2,83v input at one meter

what amp rating in watts do I need for my 

12’x14’x8’ room?

thx

I’ve tried several integrated amps for the above speakers

Peachtree 150

Arcam  sa10

Rotel A14

thx

May I suggest you look for a second-hand Sansui.  Sometimes they come up at close to your budget.  Some Sansuis are excellent and none of them are bad.  They are gutsy and can usually drive low impedance speakers very well due to their generous power supply design.