The white plastic furniture moving discs HD or Lowe's work reallywell and are very inexpensive.
That said, a pair of Monitor Audio 300 7g at $2850/pr. are Stereophile Class-A rated, have half a dozen other international awards, are fairly easy to drive with 90.5 dB 1W/!m sensitivity and a max in room output per pair of ~117dB. They only weigh 49 1/2 pounds each. Their little brother, the Silver 300 give up only a couple dB sensitivity, max output, a few Hz of bass, and weigh in at a svelte 42 1/2 lbs. I have the 300s and am extremely pleased with their musicality, range, soundstage, clarity, and dynamics. As a bonus their dual rear ports may be stuffed for final tuning. in my room, I have to place them within a couple feet of the back wall,, and stuffing the lower port only clears up any 'chestyness' on male and female vocals without sacrificing any bass.