I did not have a chance to audition 507u BUT 509x is way above all the previous integrated made by that company. Brand new league. Some likes the 509 better than 900-Series separates (google a review written by the Australian guy). I truly love it and have no urge to change the amplification for a long time.
On the other hand - let's be realistic, if you are driving inefficient (below 86dB) speakers in a larger and damped room, this amp will quickly run out of steam.
I have Dynaudio Contour 60 in my second - living room system, in a room that is closed to 30 X 20 heavily damped with rugs, soft furnitures, books, etc. When I tried Lux in that set-up, I did not get the 82dB sound pressure in my listening spot (15' away from speaker) before 509 entered "red zone" on the UV meters and sound started to be distorted.
That set-up will require something like Hegel H590 which I will be demoing soon.
Also, hearing any amp, speaker, CD player, cables etc at the dealer is truly wasting your time - I cannot stress it hard enough. Anytime you want to buy a piece of ANY gear, make sure you demo it in YOUR room with the equipment you use everyday. Otherwise you will be wasting money - example. At my dealer, Devore 0/96s sounded bright to the point of giving me headache - in my room , exactly opposite - rolled off to the point that I got rid of them, replacing with new - Super 9 design. Never, ever buy something off of other people recommendation. We all hear different and value different aspects of sound. The guys at Stereophile are heavy biased and often have totally different expectation than average guy.
