If you're looking at cheap crown amps, the class A/B x1000/x2000/xli800/xli1500 are better for speakers in my experience than the xls series. Less power on tap and much heavier but significantly better sounding units. In fact, the delta between the crown x1000 and my previous parasound a21 was smaller than the delta between the parasound and the Ragnarok. 

 I know the xli has selectable input voltage of 0.775v and 1.4v which can have slight affect on the input signal a bit. Also people never match gain structure of the amp to the source which can cause fast distortion/clipping to the inputs before the amp comes even close to clipping point and people usually like to leave amp wide open. Leaving amp wide open(fully clockwise) usually not best idea sometimes(cause speakers and sources reaches distortion much quicker and before the amp even comes close to distortion most of the time)

I didn't tell too much difference between my CE2000 and xls 2500 last time I tested and compared. I was bias at first cause the xls being class d design but, overall couldn't find too much difference. I know the xls 2500 doesn't like passive pres too much unless your source can supply optimal voltage of +4dbu. My CE2000 is same way. If I switch my CE2000 to 26db fixed gain it'll then require over 3v RMS to reach full output and with some sources sound worst than my xls 2500. Pro amps are bit more complex but, yet simple to deal with cause they're not all the time just plug n play. Matching gain structure with source(s) is very easy but, most overlooked aspect. Most common and easiest method most people do is usually leave gain halfway point and call it a day.

Im just saying overall the xls models not bad in my opinion but, do suggest if getting/trying one the xls 2000/2500 is way to go. Besides power they use better parts and better Texas instruments chip inside for crossover functions and voltage tracking. For the price they're not bad and can confidentiality say they're lot better than something like McIntosh gear. I tested my xls 2500 against pair of Boutique 600w McIntosh mono blocks and thought the xls 2500 was more true to the signal than the McIntosh gear. McIntosh just adds weird type warmness and glare to everything it's hooked up to.

X1000/x2000/x4000 are rebadged xli models for musician's friend.

The xli line is class A/B and has significantly better power supplies than the class D xls series. They also sound significantly better with decent speakers.

I know. Sam ash/guitar center( musician friend is tied with guitar center i think)has dedicated rebadge amps from both crown and qsc lines. 

I think the PSU is fine on my xls 2500 it had no issues driving ultra low frequencies at max output all day. If the PSU wasn't all that great then I wouldn't be using it as a subwoofer amp for driving ultra low frequencies and rattling houses couple blocks away. I even tried it on difficult 2ohm loads and it had no issues if that what you're trying to get at.

 I think you might be thinking of the Older xti models maybe. I know the older xti before, the home bench testing frenzy and complaints had issues with their PSU before xti was fixed by crown with the xti2 series. People were testing them against other amps and found issues testing the xti1000 with sub bass frequencies that would only output 15w@20hz before shut down. They did test the xls drivecore too and found no issues with outputting their rated power from 20hz-20khz. Forgot which site but, think can still find it.

I think I use pretty decent speakers ( I like them) which are reworked large altec lansing vott speakers. Could go into detail on their work but, I been babbling enough.