Audio / Stereo Rack

@muaythai I found myself in a similar situation recently. I just got online with Audio Advisor and ordered one of their Pangea racks. Arrived in a flat-pack two days later — honestly. I recommend calling them first. https://www.audioadvisor.com/furniture/audio-racks (not guaranteeing link will work). The racks are made of composite wrapped in some tough vinyl. Look great, and seem strong. Legs are made of steel tubing, powder-coated. Well engineered for what they are. Some assembly required, if you’ve had to put a bicycle together for your child, you should be OK. I think my son and I used a pair of pliers and an adjustable wrench. They have at least three sizes and two types; one type has steel cross-bracing, the other type lacks it. Turntable stand is the most shallow, standard audio rack should accommodate most gear. Their amp stands are absolutely massive and includes the cross-bracing. Problem is, I don’t think you can officially extend the amp stand’s height with additional shelves (but I made a way). And you can order legs of different heights to accommodate equipment of different heights on the shelves of the turntable or standard stands, but not for the ones with cross-bracing. Again, they’re serviceable, quick, cheap (<$500 each), and relatively easy if you’re mechanically inclined. They are not heirloom grade, and I wouldn’t recommend them for damp locations, but I hope you’re not using your equipment in a damp location in the first place.

Sounds like you’ve found a good vendor, this is an alternative. 

I have had a look at the link offered by @oldrooney 

The offer of the individual posts is a option that allows for creativity.

The Cross Brace Legs, can be found at 13" Shelve spacings, @ 80lb capacity per shelve, if the Vinyl LP storage option is looked at.

The description given suggests this is a stackable system, with a guidance up to 42" in shelve height @ 240lb capacity per rack. I have not been able to see how these racks use fastenings to couple together, maybe it is not a fastened together assembly when modules are added. 

Additionally, the Amp Stand has an 'X' Brace option, if this was the Base wanted for the Rack, it would need to be made known if this is compatible with the add on system, as no images show this base as the base on a assembled rack.   

As for the creativity, the Width Spacings between support posts, can be bespoke chosen, if ones own board material is chosen. As there will be potentially 4 x posts required to be purchased, this opens up the option to extend the rack to a Three x Cell per tier system. If one wants the Shelve/Sub Plinth to be produced from the most attractive material (performance wise only), the suggestion of a Phenolic Resin Impregnated Densified Wood Board to be used, has real merit. This as a material will not be bettered at the price it can be found.

Do bear in mind their are businesses now set up around offering Panzerholz as a Sub Plinth material and some are asking approx' £1000 for a board with a dimension 500mm x 400mm x 25mm.

Linn are now following Clear Audio and are using a similar type material on their £50K+ New Model TT.

There are also TOTR Speaker Manufacturers using this material to produce their cabinets. 

https://www.audioadvisor.com/furniture/furniture-accessories/?page=2

@pindac ​​​​@muaythai The fastening is done via short sections of 8mm threaded rod. Each vertical tube has 1/8” thick metal disk welded about a 1/2” from the end of each tube threaded to receive the threaded rod. The rods are prepared so they can screw in only so far. The assembly starts from the top with 8mm through bolts that feature a broad mushroom head that rises 1/8” above the surface of the top shelf and terminates upper portion of the assembly. The bottom terminates in “points” that can couple the stand to the floor through carpet; or, by use of dimpled disks about the size of a U.S. $0.05 ‘nickel,’ prevent it from damaging wood or vinyl flooring. Each leg’s length can be adjusted up to an inch or so, and a locking nut is provided. I recommend starting with each leg at its shortest and adjusting by extension, monitor what is happening while you turn the screw so as not to ‘adjust’ the height of the shelf above, not the leg beneath (don’t ask how I know this).

For the curious Do-It-Youselfers: The thread pitch of the rod is not standard, but it closely approximates 5/16”-18. I exploited this fact to add two shelves from a standard audio rack to my previously purchased amp stands. By drilling one hole and employing a single 5/16”-18 bolt I was able to secure the two shelves to the amp stand and thus terminate the lower assembly near, but not on, a leg ‘footer’ (the amp stand is about two inches deeper than a standard rack).
Employing the same trick with 3” sections of 5/16”-18 all-thread, and standard 3/4” PVC pipe couplings (which fit snugly inside the tube sections) I managed to extend 10” leg sections to 13 inches. Spray painted flat black before assembly, the couplings are virtually indistinguishable from a few feet away, and quite unobjectionable up close. I also used 5/16” x 1-1/4” boat washers to provide one of the benefits of the X-braces: the washers keep the tubes from eating into the particle board shelves. By this means I got the clearance I needed for my tallish 95 lb. McIntosh amplifiers. I wish I had painted the edges of the washers before assembly, but it’s likely a detail that only I will notice. I’m not putting anything on the upper shelves that weighs over thirty lbs., so I think I’ll be OK. I only purchased the two amp stands and one standard 4-shelf audio rack, and (4) 10” ‘legs’ (plus the 5/16”-18 rod and 3/4” PVC pipe couplings), and I have parts left over after creating two, one-of-a-kind three-shelf racks. Again, not heirloom quality, but gets the job done, and looks nice. And everything was done in a day after receiving the shipment which only took about two days —a week all in. 

@oldrooney There certainly looks to be room to tweak this system to meet a few bespoke requirements.

The 8mm Thread referred to might be a common Metric Thread Pitch for a 8mm Thread, so not Whitworth / UNC. 

Speedy Supply and  simplicity to put together are seemingly what the OP has requested as a recommendation, as they are quite delayed in their earlier made plans.

@pindac I checked the pitch at Lowe’s, and versus 5/16”-18 and it matched neither. I think I recall the pitch on the 8mm thread as being 1mm, where I figure you would need to special order a coarser thread at 8x1.5mm. A 5/16”-18 would start to thread into one of the 8mm locknuts, but could not be threaded completely through: it would jam just as it got flush with the back side.
However, it was another story with the 1/8” thick disk welded inside the leg tubes, there weren’t really enough threads on the disk to interfere, it wasn’t hard at all to force it through the first time, and then it pretty much spun free. The assembly only calls for hand tightening, and I applied all the torque of which I am capable without incident.