I love my ProAc Studio 148s and experience the same realness that you mention, especially with double reeds and strings.
Try some Soundocity SEV9 outriggers. Is what I use under my 148s. Better stability and you use a bolt and washer to mount the outrigger to the factory spike location so a gentle socket tighten is a perfect way to make sure everything is tight (but not too tight). Plus, with the "from the top" adjustable spike design of the SEV9 outriggers, placement is easy and then just screw in the spikes.
You can see pictures of this setup and my system details on my system page.
Try some Soundocity SEV9 outriggers. Is what I use under my 148s. Better stability and you use a bolt and washer to mount the outrigger to the factory spike location so a gentle socket tighten is a perfect way to make sure everything is tight (but not too tight). Plus, with the "from the top" adjustable spike design of the SEV9 outriggers, placement is easy and then just screw in the spikes.
You can see pictures of this setup and my system details on my system page.