Will adding RAM reduce latency?

I am using a yamaha DGX-630 with only a USB connection.  The latency is set at 2ms which is still noticeable.  When cubase was installed, a yamaha kx-60 with USB connection had, of what it seemed, no latency issues.  What the 2ms produces is that when the key is struck quickly then released and by the time the key goes up is when audio goes to the stereo speakers.  There is an HT Omega soundcard installed and a USB connection.
Will adding RAM reduce the frequency any further?  If not what else can be done to reduce the latency?

What drivers are you using for your HT Omega soundcard? If there are ASIO drivers for it, use them.
Have you checked in the Options-dialogue that it is the card that is being used?

The make of your keyboard has got litttle to do with the latency, it's a soundcard driver thing, and also depends on the speed of your CPU in case you use soft synths.

One essential thing is whether you're recording MIDI or audio. Recording plain audio usually isn't very latency-sensitive, soft synths and CPU-heavy VSTs are..

What N0rd said is a fact: Nobody can hear a 2 ms latency , not even 4 ms. When the roundtrip latency is around 10 ms some people in some situations react to it. That's why you should checked the drivers and settings.