Amp's that are better sounding than a nad 3020

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.

No idea what your amp sounds like but I am relegated to older stuff due to my budget. I recent scored a Denon PMA520 and tuner for about $150. One of the most pleasant surprises in a long time. Fairly detailed for its age (1990 or so) and sounds great with KEF Q150, Pioneer FS52, or QAcoustics 3020i. This is the amp that put the Sansuis and Luxmans back in the closet and started me down a spending spree of old Denon integrateds. 

I doubt you are going to find anything that sounds better than the NAD for 300.00. Save your pennies, then move up...

I think the more significant question would revolve around the age and condition of the parts in ANY 40-50 year old audio amp. If any integrated amps (including the NAD) have been serviced by a reputable repair shop then one can do a comparison. If I were looking at what I could buy for $300 and many older amps were found, I must include another $300 for service and parts at a minimum. If I didn’t take into consideration parts condition, parts availability, quality service.... that would be foolish. I think an amp for $300 is really an amp for $600-$800, or you will have failure problems very soon for buying an old integrated amp for $300.