Should I build plinths or screw spikes into cabinet?


I've got a great old pair of B&W DM640 floor standers, but I don't have the plinth and spike kit that were sold as an option back in the '90s.  Since I have been unable to track down a kit online or directly through B&W I am planning on building my own.

The speakers themselves were built without any isolation system on the base of the cabinet, and were set on top of adjustable "lugs" which were incorporated into the top of the optional wooden plinths.  Each plinth had four basic spikes mounted at the corners.  This sounds easy enough to replicate.

Does it make more sense to simply drill into the base of the cabinet and mount the spikes directly?  The tweeters are nearly at ear level, so I don't need to lift them much.  I am a little hesitant to make any permanent alteration to the speakers, however.  Any opinions or alternatives are welcomed!
guitared
Hi BDP, I've done exactly that with each of my components and could not believe the improvement they made.  I'm using marble tiles instead of plywood, it was actually cheaper!  I also have marble tiles under the speakers and above the homemade rollers presently, and every aspect of the sound has been improved over just spikes on the hardwood.  I'm a little unsure about adding the inner tube under the speakers for stability reasons; the system is in a living room and I'm worried someone (or some dog) will knock them over.  

Has anyone tried this with a more traditional floor standing speaker?  I may get 2 more tiles and try sandwiching the tube or rollers between them.  The cabinets are rectangular so I need the tiles to allow placement of the rollers in an equilateral triangle.
I'm anti spike for speakers since putting Vibrapods under my Silverlines. Keeps them independent of floor vibes and they simply sound better than they did with spikes.
When guitared posted he reminded me of these: Ingress Engineered Products. With some flagstone or similar product on the floor it could be done.

All the best,
Nonoise

The Ingress are the best deal around in roller bearings. He now offers a version made to Barry Diament’s specs: a highly-polished single cup made of 7075 aluminum, with a large diameter, shallow bowl (the result of machining the shape of the bowl to follow the curve of a very small section of a very large sphere) to achieve a very low mechanical filter corner frequency (of around 3 Hz), and 3/8" ball bearing. $90 for a set of three, half the price of the Symposium Acoustics Roller Block Jr’s, and of a superior design.

I've just about accepted the fact that I'm getting two sets of three Seismic Pods to put under the Sound Anchor stands my ET LFT-8b's are on. About $800-$900, but justified by the degree of improved sound (or so I've been lead to believe ;-).

guitared, You should go under your house, find the area to support with bottle jacks and 4x4's. (or equivalent), After this, (if needed),you may look at look at other options above.

(All of this will keep you under your $100.00 target... I'll make a bet that it will be the ticket...just requires some effort.)