Hopefully this will answer a few questions for other 520 owners. Not being an expert, and not having done a "double blind" test I will just share some observations over the next few days (as time allows). Opening the box and taking a first glance: The two are very different receivers. Looking at the front, all looks quite familiar, but standing above them and looking down, things are not even close. There are 2 circuit boards visible on either side of the 525 (which is divided in two by a metal housing running the entire depth, which contains the infamous fan). Of course, the back would look different because of the extra channels of the 25 and the lack of main "ins". And, what's this??? A power cord! A real power cord that detaches completely (so you spend a zillion dollars on a "good" one, if you want). The cord is made of real power cord stuff, not the glorified Romex-like stuff on the 520. Feel: The 525 has a fairly even weight distribution. The 520's wt was primarily on the Left side (right side, if picked up from the back). Additionally, the binding posts of the 525 have a more solid feel than the 520. Sound: In the brief time I've owned it, I've not had a chance to spend much time here but.... Detail... It just seems to have a more detailed sound, but remains warm and inviting. I have a very poorly matched set of speakers, but it does wonderful things with both 2 channel and multichannel sound. For mains, I use Linn Index+(, Klipsch KSC-C1 center, and Klipsch kg1's for rear. If I ever go to 7.1, I'll use Boston Acoustic HD5's in the rear center). The 2 channel sound coming from the Linn's is what I used to hear in the days before they were moved into my home theater. I loved what I heard from the 520, but the 525 is a full step up. Home theater is more detailed and better separated. I watched "Signs" the other day. The knocking on the doors, running through the attic, and other sounds that were centered away from the front channels were very realistic. It came through with a great image... But I never watched this movie using the 520.... Poor test, but I warned you... Bass management may account for much of the above. I have played with it some so can't recall exactly where my settings are, but I believe it's like this... Mains: 40db Center: 80db Rear: 60db Sub + LFE Anyway... While I could live with the 520 and consider it one of the better A/V receivers made (capable of both good music and home theater), I like the 525 even more. There seems to be some slight decrease in the available power, but nothing alarming and what is available seems less distorted...music being more musical and theater imaging better. The seemingly slight decrease in power could be less distortion at the same volume.... Again, no A/B testing and memory is a poor reference. I can say, without question, I liked what I heard. There also are some things I find annoying: 1) The binding posts are too darn close together, as are the power outlets. It makes hooking up speakers tedious, and my Terk Pie antenna is covering both outlets. 2) There is a pause as the receiver auto-switches from one audio mode to the other on a DVD (i.e. DPL II to Dolby Digital, or DTS). This means you miss such important things as the first few seconds of the THX intro........ I know....... but it really is annoying. It doesn't seem to do this if you go back to the menu and then back to the movie; only on the initial startup. 3) NOT the fan. I haven't heard it and have run the receiver fairly loud for about 4 hours straight. Afterwards, the unit was left on. The stand gives about 1-2 inches space above the unit and the back is completely open around the receiver, which is flush with one side of the cabinet but is several inches from the other side. You're gonna think I'm crazy, BUT.... I like the remote. It feels pretty cheezy, but it can be fully programmed, is back-lit, and is a major improvement over any Denon remote I have ever handled. It is logical, can be set for "punch through" features (so you don't have to go to AVR to control the volume while watching a DVD, the VCR, etc.), has a feature that will search for a code if you can't find the right one (for your other components) in the manual and is easy to set up. It's probably exactly the same as the remote for the 520... Uh... I liked it too. If I could not get all my money back for the 520, I'd never consider changing receivers. I am pleased to say that I can and feel it's really worth the extra $100... At least that's how I feel today. Will play with it for another week or so before my final decision.