Hi Thomas,
I haven't played either of them, but I do own a dxg305 piano. I would imagine the sounds would be similar to the 293/295.
Keep in mind a couple of things. The 293/295 midi interface is via usb, which is usually easier to set up than using midi cables etc should you you ever want to midi the keyboard to your computer. You should therefore check how a psr290 connects to a computer ? It may be via usb also, but I doubt it.
Second point, PSR293/295 don't appear to have a facility for loading additional user styles? if that's the case, you're stuck with the styles that are in the keyboard.
The PSR450 appears to have a floppy drive for loading styles, but it doesn't appear to connect to a computer via usb. It usually ends up being a bit more costly & difficult to midi up to your computer, should you wish to do so.
Having said that, should you get either a 293/295, down the track if you decided you did want to have additional styles you could connect your keyboard & computer together and use software like One Man Band to play your styles ie you use your psr 295 for sounds & keys and one man band ( OMB ) for your styles. Your inexpensive keyboard doesn't have to become redundant as your needs grow.
Another option may be a dgx305 or 505. They both connect to computer via usb interface. They can load one user style only ( which is a bit of a pain, but better than nothing.
I use One Man Band software for editing my psr/dgx user styles. I also use it as an arranger midi to my computer/dgx.
Below link to a yamaha site, you can dowload specs & manuals for the keyboards. Do a bit of a comparison, you don't want to dash out & buy the wrong one.
http://tinyurl.com/8ruck http://www.yamaha.com/yamahavgn/CDA/List/ModelSeriesListLE/0,,CTID%253D205100%2526CNTYP%253DPRODUCT,00.html
Below is a link for the software I mentioned
http://www.1manband.nl/omb.htm For people that have their computers midied to a keyboard, it can help turn a very inexpensive keyboard into a full fledged arranger. It doesn't improve sound quality, polyphony etc but it does give you access to user styles & style editing, sequencing etc which is after all what arranger keyboards are about.
Take your time & do your homework.
best wishes
Rikki