interesting thread....the screws into floor boards does more than provide an easy way to level the speaker. it decouples the speaker from the floor and improves the bass.
our flat in london had floor boards, using a pair of b& w 602,s on target stands the bass was boomy, in short unlistenable.
4 pozidrive screws through the carpet and sit the spikes in the cups of the screws, i also did the target rack i have, massive improvement, solid bass that you could feel, no boom. it works......
the house we rent now has a solid laminate floor over concrete, the dali suite 2.8 floorstanders i now use are spiked and sit on atacama spike shoes, as is the target rack....