New Integrated amp recommendation

Here are Stereophile measurements from the 228Be that likely has similar specs to your speakers, and given this I’d want more juice than the 505z can provide…

My estimate of the F228Be’s voltage sensitivity was 89.1dB/2.83V/m, slightly below the specified 90dB/2.83V/m but within the margin of error. The impedance magnitude remains below 8 ohms for the entire midrange and bass, with minimum values of 3.42 ohms at 98Hz and 3.55 ohms at 290Hz (fig.1). There is also a demanding combination of 5 ohms magnitude and 39.5° electrical phase angle at 390Hz. While its nominal impedance is specified as 8 ohms, the Performa F228Be would work best with an amplifier that’s comfortable driving 4 ohm loads.

Given what you’re looking for I was also gonna recommend you look at the Coda CSiB and saw this used one available, which if I were you I’d strongly consider.  Hope this helps, and best of luck.

https://www.usaudiomart.com/details/650239771-mint-3yr-old-coda-csib-integrated-black-v1/

+1 on Anthem STR. I had it in my system for a couple of years and found it to be an excellent choice for the money, but also an absolute terms. Produces  a natural, detailed sound, well powered and superb build quality. Worth checking out

Having owned a Musical Fidelity Nu-Vista 600 I can say this integrated should be in the discussion. 
Only sold because the 80 pounds was too much for me to handle after a major leg injury. 
I would buy one again. 

PrimaLuna EVO 300 hybrid integrated. The change out all the preamp tubes to NOS.  Contact Brent Jesse

I am using Amperex 7316, Telefunken, and RCA Clear tops

Accuphase Laboratory, Inc. Aka Accuphase intergrateds are the real deal. I have a Rogers tube intergrated also recommended.