feet and legs

Get Machina Dynamica Promethean Springs, cut your 4" in half and make a sandwich. You will have a fabulous equipment base

One caution about the V-pads or similar cork-between-rubber isolation devices.

They work well from an isolation point of view but the black rubber surface on them will leave a large, very permanent black mark on any wood surface they are in contact with for awhile. I would suggest a layer of plastic wrap or something similar to protect your wood floors.

Don't know if you can find someor have it fashioned to what you want, but Iron Wood, yes there is such a thing, is about as dense as it gets and as heavy, Ebony is right up there with it. Check it out, if it will do what your looking for, you can stay with wood

Thanks for all the great responses so far. I'll try some out and report back.

I highley recommend the Mystery/Super Mystery feet from Marigo Audio.I use them under all of my gear. They come with a 30 day money back guarantee.

Hey why not place truck inner tubes under the slab of maple. I would place one on each end and one in the middle.

One of the most effective woods I've tried in combination with my maple slab is Zebrawood, available at wood specialty stores. But I use it above the slab between it and the component.

I have my 2" wood slab supported on top of my vintage wooden credenza (a real no-no for audio components, supposedly) with V-Pads, available at heating and air conditioning supply stores. Although they absorb floor vibes they do not deaden the sound in the least. V-pads are devices of cork sandwhiched between ribbed rubber surfaces - identical to the devices Mapleshade recommends for their maple slabs, but larger. They're actually quite firm in resiliance. The V-pads available from HVAC stores measure 4"x4"x1". They hold quite a bit of weight, you can stack them, and use several stacks along the length of your slab to support your entire set-up.
I actually replaced the solid brass speaker spikes on the bottom my Von Schweikert VR4JRs which rest on a carpeted suspended wood floor and noticed a significant tightening of bass - which really surprised me since conventional wisdon is that spikes are best.
And, they are dirt cheap. About $3.00 apiece. So it is an inexpensive experiment - say 5 each along the front and back lengths as well as along at the midpoint length of the width for a total of 15 and a cost of $45.00 If you like the effect, and also want to increase the height just stack them up. Don;t let the ultra low cost muslead you. They are remarkable effective. They will also protect your hardwood floors.
Let me know if you can't find any; I may be able to help you.
My configuration is the credenza with v-Pads on top, then the maple slab - with spiked component on top of the slab. Resolution is outstanding.