I got a Cambridge 640P a month ago and it was so much more revealing than the Amber Model 17 preamp (which was a vinyl enthusiast's preamp) that I upgraded the line stage, am getting new speakers worth five times what I'm listening to now, and am contemplating biamping with faster, fresher amps.
So I guess you could take this as a blessing or a warning. I had a pretty good equilibrium, but I wanted more--more separation, more inner detail, more extension at the frequency extremes, more dynamics. For a mere $169 the 640P added that beyond my expectations, but then I wanted to see where that extra resolution would take me, so I upgraded the cartridge and liked what I heard and wanted to see how the rest of the system could scale up. So new floorstanding speakers with 250w handling capacity are in transit and I'm shopping higher powered amps (I believe in a higher power, in fact, the higher, the better nyuk, nyuk!) and the extra speaker cabling to make it all work.
So maybe you need to stand pat and enjoy the system balance. There's no doubt in my mind that the 540P would CREAM the phono unit in almost any receiver, but it could set you on a new multi-thousand-dollar path to upgrade like it did to me.
OTOH, I find my system more compelling than ever, and have no doubt that I will enjoy it even more for big band, large scale orchestral, and opera when the speakers arrive and I get a few hundred extra watts to drive 'em.
