"You know, you have a point about the two keyboards looking better. 
DonM"
I also remember the other side of the fence.  I was playing at a wedding reception using the PSR2000, two JBL Eon 10G2's, X stand and boom mic, and someone said, "it sure doesn't look like much does it". And of course I would have to agree with that. It really didn't look any different than the $100 Casio at WalMart.
The other thing for me, is that I don't sing, so I need all the help I can get to justify getting a lot of money playing out. While I play fine and really only need one good one, it also make me feel more pro and I think that transfers into my playing and does affect the attitude of the audience.
At one time I used to go out with three keyboards only because I got "deals" on them, none of them were general midi and one was really a "beater".  I used to use the KN1000, Roland E35 and a Yamaha PSR320(?). I have pictures of it and even though these were not the greatest keyboards except for maybe the KN1000, it had that "pro" kind of look.
I also remember thinking how great it was to be able to walk in with the lightweight PSR2000 and Eons and how quick it was to set up, but, I really do think that two or three keyboard does enter into the psychology of influencing yourself and the crowd.
Scott