I also owned CASIO WK-1630 for 2 weeks and returned it to the store. The internal speaker is very nice and loud. The registration memories are also quite usable. BUT after listening to the voices for a week, the voices are THIN compared to other models. It becomes unbearable after a while. I noticed this on the grand piano. The electric pianos are not usable IMO. Access to voices and commonly used parameters are also a bit awkward.

YAMAHA PSR550 is usable, decent and can be used for pro use, live use, over the amplified speaker and you will have a decent sounding system. But it costs around $500. I know squeak in this forum will part with it for much less.

Other alternatives are Yamaha PSR1000 or a used PSR2000. All can be had for less than $700 these days. This system is used by pros BUT the key feel is terrible IMO although some pros seem to be OK with that.

It depends what you are going to use the keyboard for. If for home use and composition then you probably don't need registration memories or quick access to parameters as much.

I bought all my kybds at Guitar Center and if I don't like it, I return it within 30 days. It has worked out great ! NEVER buy a keyboard without trying it out for 1 week or two. You will discover its weakness in that period of time and you will be thankful that you can still return it without any financial loss but your time.