Not sure what you're after with this question but it's kind of like asking if all season tires were just as good as summer racing tires. For most people, as long as they're round and hold air, they are equal. For a racer, he'd prefer the racing tire and appreciate the advantages it offers.
For audiophiles, most will say as a rule, an amplifier is going to sound better than a receiver. The answer is in your question... a receiver's has several functions, and only one of those is amplification. An amplifer has 1 function.
If I buy a $500 receiver and a $200 amplifier, I would expect the amplifier to still be better. What do you consider 'midfi'? I have heard $1,000 receivers that sounded pretty good... almost as good as a $500 amp ($200 used)
For music I'll take any amp, any day. For HT absolute sound quality is less important and the price difference isn't as valuable as it is in 2-channel to me. So, receivers are fine for me in HT.