Hello to all fellow members. This is my first thread and posts. Recently, after a lot of research, I purchased a pair of AKG K495NC headphones for portable use with my MP3 player, without listerning to them first. I have access to some Sennheiser PX100's and a pair of Beats SoloHD and the 495's outperform both nof these headphones easily but there are some aspects to the 495's perfoprmance that have me wondering if in the end I made the right choice or not. Before purchasing the 495's I was able to listen to the B&W P5's and the Sennheiser Momentum headphones, without the benefit of a direct comparison to the 495's, and by memory alone I feel the 495's are still better sounding than either of these headphones as well, realizing full well that this type of memory can someitmes be untrustworthy. Here's the thing. Initially I was going to purchase the K550's but my concerns with that model that being their size and weight ( in regards to portable use), the lack of a carrying case, a non-removeable cable, and most importantly questions as to just how well my MP3 player could drive them without an outboard amplifier were giving me pause. Then I saw the 495's which addressed all the concerns I had with the 550's. The noise cancelling was a non-issue either way, so I decided to give them a go. All the files on my MP3 player are in uncompressed PCM WAV, as I find I can hear a difference between this and even 320kbps MP3 encoding. My MP3 player is a little older and does not support FLAC. Like I said I certainly like the sound of the 495's, for the most part, their build quality is top notch, and I got a very good deal on them, but there are a few things about their sound that bug me a little bit. They, first of all, sound like two completely different sets of cans when NC is engaged and when NC is turned off. With the NC turned off bass is practically anemic, no matter how much fideling I do with positioning. With the NC engaged the bass while deep and powerful is a little one note sounding and a little overpowering resulting in some obscuring of the mids and highs. I also find that while the sounstaging is good, there is to me at any rate, a little disconnect in the imaging. A sense of the soundstage not being a single entity so to speak. It's like the sounfield is too spread out which presents a sort of lack of coherence. Vocals sound fantastic with these headphones and the dynamics are excellent but I feel that there is something mising as far as overall refinement and clarity in the sound of the 495's as well. The headphones are admittadely very new, with only about ten to twelve hour of use at this point. I did notice a considrable amount of improvement in the sound of the 495's within the first couple of hours of use, thank god, because they sounded very flat and uninvolving right out of the box, but have heard no noticeable change in character since the first few hours of use. I am wondering if despite the misgivings I had about certtain aspects of the K550's if they would not have been a better choice for me overall. The truth is the most important aspect of any pair of transducers I will purchase is ultimately sound quality. All other considerations are secondary. I can live with the other shortcomings of the K550's, that I mentioned earlier, if they in the end sound better than the 495's. Has anyone here had a chance to directly compare the two models? Are my concerns about the 550 valid, in particular concerning their ability to produce good sound driven directly from the output of a portable device? I have the option of returning the 495's and doing a switch for the 550's with the retailer I purchased the 495's from. What do you people think? Will the 550's give me the increase in overall sound qulity I am looking for in comparison to the 495's? Unfortunately this retailer is mail order and I won't be able to audition the 550's before making the decision.