Went back to the music store today. They STILL don't have the PSR-E463 on display -- even though they now appear to have completely sold out of the E453, as I didn't see that either. They still just had the E463 bulk-stacked in boxes. But, I did take a quick look at a few other boards there...
Casio CTX-5000...
Yes, the big kahuna was there now. Sounds like the CTX-3000, which is to say, very good. From what I've read, there are significant differences between the 3000 and the 5000, including more reverb and chorus settings, a higher powered amp, and the modulation button, which all go toward justifying its 50% greater price -- $450 instead of $300 US. And, I played around with the DSP settings to try to edit them, and yes, I could get into some submenus that appeared to be fine-tuning the DSP settings. And I'm sure that this is the kind of thing an owner would get used to, but in my opinion, this feature is anything but user-friendly or intuitive. All of the menu controls are shared with a numeric keypad, giving these buttons multiple functions, and nothing was labeled clearly enough for me to determine how the parameter I was adjusting related to the DSP feature. For example, I got a cool echo-y piano/strings sound, but I have no idea how I really got to that sound. To me, its a big difference from the PSR-E400's, which all but invite you to play around with the sound with the live-control knobs and the logical way that those knobs' functions are assigned. The key feel is similar to other recent Casios, which to me is a little spongy, but I did get used to it as I was playing around with it
Yamaha PSR-F51...
This is an extremely basic keyboard. It is not touch sensitive, and it has a sound-set reminiscent of Yamaha's basic boards of the early 1990's, and also reminiscent of that time period is the basic numeric LED display that indicates your settings. There is no direct control of reverb or chorus, and the sound, while not bad, is a bit thin. It seems to me that the only reason to get such a keyboard would be for someone who wants to maybe buy it for a kid to see if they have an interest in learning to play before investing any more money, and that this person would want the absolute cheapest new keyboard available that has a good, well-known name like Yamaha. Otherwise, it would seem that the PSE-E263, for $20 more than the F51's $100 price, would make more sense.
Yamaha Montage 6...
They finally got this bugger hooked up! No way did I have the time to figure out how to edit the sounds, but I'm sure all kinds of editing features are there. As expected, there are just hundreds and hundreds of sounds. You call up a sound category, like "piano" or "organ", like normal, then a list of sounds appears on a touch screen. And then you can scroll down for more sounds in that category. And more. And more! It's what you'd expect for $3000. But honestly, some of the sounds did not sound any better than what I've heard on the PSR-E series, but of course, others were far more intricate. There was an interesting jazz vocal sound, which played various doo/wop/etc. type of scat sounds as you played the keyboard. And interestingly, as I played up and down the keyboard, the same key would produce a different scat syllable. Not sure if it was due to how hard I was playing the key, what notes I played before it, if it was random, or if there was some other guiding parameter. One important limitation: When I selected a new sound to play and then hit a note or chord, the keyboard did not respond right away. It took about 1 second for the keyboard to set up the new sound before I could play it. If this holds true with registration or performance settings, that could be a considerable drawback when playing live.