One thing that would help is a larger aperture, this helps get more photons to the eye. However, the larger the scope, the more it costs.
An alternative to what you want to do is a camera does video ingratiation. Still expensive ($900 to $1300), but it'll take a stack of video frames (at 1/30th of a second) and sum them together into one image. Which is near real time (delayed by a few seconds).
http://www.optcorp.com/product.aspx?pid=319-325-9051
http://www.optcorp.com/product.aspx?pid=319-325-9300
Here's an example of what you can see -
http://www.epcinternet.com/astron/StellaCam/Images.html
If you're interested in just planetary, lunar or solar images, then get an planetary imaging camera.
http://www.celestron.com/c3/product.php?ProdID=354
You'll need a laptop or netbook to capture and store the images, but this allows you to capture a series of frames, pick out the best, stack them into something that looks nice.
http://www.astronomie.be/registax/
http://www.astro.shoregalaxy.com/webcam_astro.htm
Also, for more help with the ETX-90, check these folks out -
http://www.weasner.com/etx/menu.html