2" thick solid wood shelves add great expense. I also considered doing this but the materials alone for some of the less expensive hardwoods maple and cherry are quite expensive for 2" stock material after doing some pricing on the raw materials, things have really gone up since my last project! The Core designs are beautiful latitk and the prices while not exactly cheap are certainly solid. The Timbernation racks look real nice for the money and I’m sure just as solid. What is nice is that this guy will build exactly what you need as he states in his ad with demonstrations of other products that he builds and shipping is free. Since much cherry and maple hardwood comes from this part of the country he probably gets it cheaper than what it might cost in other parts of the country. Certainly his prices seem to reflect this, something to consider Rebbi if you are looking at a CUSTOM wood rack to meet your needs. Another option is Sound Anchors, Bob who is local to me will build whatever you want. The problem is shipping as his racks are welded tubular steel and filled and power coated but so far as outside vibrations I would bet better than wood. Wood is an excellent choice when used with Stillpoints or other vibration isolation controls if this is a further consideration aside from stability. 2" thick stock is just not necessary for supporting a 55 lb amp if you have budget considerations.
Another budget option is 1.5" thick yellow pine which is readily available at local home improvement centers, can be laminated to the depth desired and is not nearly as expensive as the hardwood option but is VERY strong and stable. You could find a local woodworker or you could do it yourself if you have access to bar clamps, a doweling jig or biscuit jointer, a 7" saw and a hand plane or jointer and a finish sander. I know this might sound intimidating if you are not famaliar with woodworking but it could save you a ton and the journey to discovery is always worthwhile. Aesthetically, pine might not be a pretty but staining is another option; beauty is always in the eyes of the beholder. Legs could be 2X4 pine or threaded steel rods.