I have a Slik Pro 700DX tripod. It's heavy but ridiculously stable and solidly built. They go for about $140.

What don't you like about your cheap $20 tripod? Unless it's completely rickety at the head or something, you might be surprised how much stability can be had by simply adding weight to the bottom of the center post (hanging, assuming it has a hook).

It's really a weird topic. The more light you have, the more shutter speed you need and the less stability you need. In well-lit situations, I consider any tripod nothing more than something to hold the camera.

I got my new one due to shake caused by wind and needing to take 1/2sec shots at night with poor lighting. The head on my cheapie sucked and would vibrate in the wind, so no bagging helped.

Just saying...