@yogiboy I'm by no means an expert on this kind of stuff. So, I can't explain, from an electrical engineering vantage point, why this is. I've had experts explain the science to me and read some stuff about this, but I still don't get it. However, from personal seat-time experience auditioning speakers & power sources, I've found that less than 8 Ohm nominal load speakers, even very efficient or sensitive ones, tend to crave current in order to perform their best. Although the Levinson 383 seems to have a quite robust power supply (i.e. double the watts from 8 Ohm to 4 Ohm), I don't know if it could generate enough current to make most less than 8 Ohm nominal load speakers in the OP's budget range truly sing? Would it be enough to drive a lot of less than 8 Ohm nominal load speakers? Yes. However, there is a big sound quality difference between just having enough juice (i.e. current) to drive some less than 8 Ohm nominal load speakers and making them sound their best.
Here's just one recent example of what I mean. I won't cite all the specs involved here. You can look them up on the web if you are so inclined.
Several years ago, during a several months' quest to update my two-channel system speakers, I fell in love with a pair of Aerial Acoustic 6T (i.e. 4 Ohm speakers). When I heard them through a big MAC 75-watt tube amp with power (i.e. current) to spare, they sounded just heavenly. However, when we switched to a 100-watt MAC SS integrated without Autoformer, it took about 5 seconds for my ears to hear the little MAC just couldn't deliver enough juice (i.e. current) to make those Aerial sing. It had enough to drive them and still make them sound very nice indeed, but not enough to squeeze everything out of them that they were/are designed to deliver. I've had the same experiences, over the years, with other mismatched amps & speakers.