Best Receiver for “Mid-Fi” System?

It's over your budget, and maybe above mid-fi, but Marantz SR8015 was last gen TOTL receiver. They have been closing them out for $2k, you will not get a better receiver for this price. 

It's heavy and huge, if you let it run in class A mode, it will run really hot. This is what is in my HT room, it works flawlessly, is ok with music, and can drive lower ohm speakers, but will generate heat. Tested it out with new KLH Model 5, 6ohm, worked just fine.

The latest generation of better Sony receivers have a greatly upgraded HDMI input section, so an STRAZ5000 would be my suggestion.  The amp is a beast also.  Dust off your audio engineering degree, though...its packed with options.

You can try any of the Anthem AVR recievers they are very highly rated and also come with anthem room correction.

I see a lot of the mainstay receivers, and that's OK.

I also see a lot of commentary on your speakers and what it may take to drive them properly...

A: Get a honking receiver! Remember they all say. "xxx power, 2 channels driven.

B: get a decent receiver, in your price range, but add a separate power amp to drive the tough load of your speakers. Also, an external separate power amp, would likely make it all sound better.

I my past days of using an AVR for music listening, the large revelation of a separate power amp was significant.

https://www.crutchfield.com/p_033AVS970H/Denon-AVR-S970H.html
$900 or as low as $811 in "scratch and dent" they are pretty good with their checkups on returns.

Anthem make some of the very best surround sound receivers. They’re a bit pricey but well made & sound very good. I’ve had my 7 channel one for several years now , it works flawlessly, sounds very good & quite powerful.