Mars is a poor beginner's object even when closest as it is now.

Contrary to the pictures you see of Mars, visually it is a rather low contrast object. Most beginners see little but the polar cap(s) at first. It takes time to train the eye and brain to see the low contrast detail. One hemisphere of Mars is especially void of detail. Though if you were viewing at about 1 hour UTC tonight (7 p.m. CST) Syrtis Major, the highest contrast feature on Mars besides the polar cap was well positioned in the center of Mars but Mars was just rising making it too low to see. Wait for it to get high over head to get the clearest view, though by then Syrtis Major will have been replaced by some other features, but still ones of fairly good contrast. Mars rotates about 40 mintues slower than we do. By Christmas night Syrtis Major will be nearly centered on the disk of Mars about 5 hours UT (11 p.m. CST). Then assume about 40 minutes later each following night.

There are several places on the net you can see what is "up" on Mars for any particular time. One is at the Sky and Telescope site: http://www.skyandtelescope.com/
Scroll down to Mars Profiler.

There are better ones but I don't seem to have them bookmarked.

Also you may be pushing the power too much, a typical beginner error. Contrast is what you need. Too much power for the atmosphere's seeing conditions just ruins seeing low contrast detail. When the atmosphere is very steady and the image doesn't go in and out of focus constantly, highest contrast is at about a 1 mm exit pupil. You are running 0.6mm. You're eyepieces are limited but try the 20 and the Klee for a 1.2mm exit pupil. Or just the 10 for 1.7mm exit pupil size. It will be smaller, and yes it is already small, but you'll likely see more once you get used to it. You have to learn to grab that split second of fine seeing the atmosphere gives you every once in a while. The great photos are taken by taking hundreds of images up to 30 or so a second, then sorting out those few that give the moment of good seeing then stacking those, pushing the contrast way beyond what the eye sees, applying sharpening routines to that and the result by those good at it is a great image but not what you'll see at the eyepiece.

Use the moon that's out to judge your seeing. Looking at craters near the terminator see what power gives you the sharpest image and highest contrast and then use that on Mars.

Some nights have such bad seeing nothing is sharp and clear. That is especially true if the jet stream is overhead or a front has just gone through and there are still lots of variations in the temperature of the air with a zillion pockets of warm and cold air that haven't yet evened out. If the stars are twinkling like crazy (doing the jitterbug in my astronomy club's terminology) it's not a night for planetary viewing. I get nights where 50 power is the maximum the atmosphere will allow. Rarely can I go over 250x, 0.8mm exit pupil for your scope.

To determine the exit pupil size divide the focal length of the eyepiece by the f ratio of your scope (6 in your case) then if you use a barlow divide that by the barlow power ((20/6)/2.8=~1.2. To convert to power divide 200 (your mirror size in mm) by the exit pupil size (200/1.2=~167x. There are other ways of doing it as well. I find this the most useful.

Have you collimated the scope since it arrived? They never seem to arrive in collimation. Super accurate collimation isn't needed at f/6, a sight tube should suffice.

Rick