Hi, putz. You shouldn't have any problem on berber carpet. On very thick carpet with spongy underpad, Giant Gliders allow easier mobility of the speakers but either way you'll have very good lateral stability. Salk HT3 speakers have a considerably wide footprint relative to their height and plenty of heft, so I can't really imagine them being tipped over by accident or any spikes slipping out. When you move the speakers, push from a low position and take it easy as you go--not like pushing a shopping cart around or anything.
As WGH suggests, Threaded Stud Gliders are an excellent option to accomplish the same isolation/decoupling of the speakers, especially if the floor gives much resistance to the speakers sliding. With a superior isolation/decoupling approach, there's scarcely ever any real need for spikes at all. With dBNeutralizer isolation provided by either of these Gliders, you should get a more linear and better-defined bass with deep extension and subtle all-around improvements throughout the audio spectrum.
Any difference in sonic results between brass and titanium Gliders is most likely to be subtle. Might not be apparent right away in an A/B comparison manner, but prolonged audition will usually give an appreciable thumbs up to the titanium Gliders, maybe just a little less listening fatigue, perhaps nothing you can really put your finger on other than just a more relaxed and engaging musical experience. Of course, comparative differences will vary from one system to another; differences might be virtually inaudible or could be quite profound. Depends somewhat on how the metals interact with the spikes they're being used with and the overall micro-vibrational environment. Titanium tends to do the best with taming higher-frequency acute vibrations that contribute to audible glare.
Steve HerbelinHerbie's Audio Lab