It sounds like your main perceived deficiency is the lack of bass. For your "going forward" proposition you could get a subwoofer (maybe a B&W ASW610XP) that will mate well with your system, use the DM602S3s for your surrounds and get some B&W DM604S3s for your main speakers.

As for the speaker stands, if they are fillable, try filling them with clean sand. Some people even alternate lead shot and sand.

SVS makes very musical subwoofers that mate well with most loudspeakers. The SVS PB13-Ultra will eliminate your lack of bass.

That all said, I would not create a 5.1 system for dedicated music listening. I would figure out a total budget and then audition stereo systems to fit that budget. Loudspeakers 1st and then amps that sound good with the chosen speakers 2nd. If the music is truly your first priority you will need to listen to equipment so you can identify what will satisfy you.

i think that some forget the most important aspect(more important than any speaker or equipment) is the *room*!!!

if it were *me* i'd treat the room, fixing peaks/nulls/standing waves first, and *then*, and only then, worry about equipment. if your room is not sorted, the equipment isn't going to matter because it wont perform as it should anyway.

1. Is it worth sorting the stands out with complete spikes and cones for the speakers?

You need spikes for the stands and blu-tak to anchor the speakers to the stands.

this is due to the fact that the accelerations of the box, as imparted by the high accelerations of the drivers - must be countered in order to properly express the correct dynamics, which begets the inevitable perceived increase in bass quality and overall coherence of the perceived sound. This is the result when the speakers are properly anchored to the stands and the stands properly coupled to the floor. IIRC, a tweeter moves at up to 40g's of acceleration. Woofers are much slower..but they have considerably more mass and they do move it very fast, relatively speaking.