Oh wow, that's a serious beauty that Soundcraft Five series. With 54 frames you mean 54 faders? That's a beast of a machine!
Misspoke...it's actually a 52 frame. This means, yep, 52 faders besides the center routing/master section...48 mono, 4 stereo.
Hold on... 400 lbs that's I guess getting close to 200 kilograms! That's a serious thing, did you hire a crane to first remove the roof of your house and then let the desk go down into your house or how did you manage to transport such a beast? I live in that kind of cheap build new houses where everything is built just at minimum specs to keep the house standing but that's it, I think if I would put somewhere a 200 kg mixer I think it goes through my ceilings ending up flatting my coffee table in the living room! ;-)
My house is fairly typical mid-century suburban construction, with the section the studio's in dating from 1971. This is about the end-point for codes standards that would let you put something like this in without eventual structural damage. Further on into the 1970s, structural codes started to get lax, so that by the 1980s you wouldn't DARE do something like this. Plus, the whole thing, plus the patchbays and the computer work surfaces are on a large, multi-part BenchPro Dewey setup that can hold 2 1/2 TONS per unit. It ain't goin' NOWHERE!
FYI, see here for BenchPro stuff. When I got mine, they still sold direct, but you can find their stuff here: https://www.gotopac.com/benchpro-workbenches
As for these sort of things not being around im Deutschland, check THIS out: ujAAAOSwJ5BeHEks" target="_blank">https://www.ebay.de/itm/Mischpult-Allen-Head-ML-3000-832B-Kanal-Live-Mixer-mit-RPS-11/174154405138?hash=item288c695512ujAAAOSwJ5BeHEks It's in Baden-Baden, only EUR 1500. The Allen + Heath ML series was also in the running here for the upgrade, and while I was looking at the ML 5000, the 3000 is its little brother. And this thing is CHERRY...yeah, the deals are out there, just have to root thru the dross to find the GOLD.