I could use some help.

I'm in the market for a universal remote control to handle my Denon receiver, Sony DVD player, Panasonic TV, Marantz CD changer and a JVC VCR. I've been thinking that the HTM MX-500 might be good but I keep reading great things about the 15-1994. I am a little confused though - are all the buttons learnable or only the "smart keys". Also - please forgive my ignorance - what exactly are advanced codes and discrete codes? I would love to be able to get away with a $30 remote that could do most, if not all, the things I want it to.

Any help would be appreciated. Thanks!

You can learn to any button except for SLEEP, FAV/SCAN, and the buttons. There is only enough memory to learn about 20 buttons total. Advanced codes are functions not originally assigned to buttons by OFA/RS, but which the device will understand. You can assign them to any button except the device buttons. They use a different area of the memory than the learned buttons, and you can set up about 46 of them. Discrete codes are non-toggle codes for power on, power off.