First off, 2 rj45 per room and 4 in the living room seems to me as excessive.  Yes, a hard line is better then wifi, but that's a lot of copper to put in "just in case" when small hubs are cheap.
Second, and more importantly, you don't want a rack.  Racks and rack mount gear are sexy but only make sense if space is really tight.  Like in a colo rack or if you have 1000 servers.  Plain old tower cases on a shelf is more then adequate and costs a lot less.
In my basement I had two closets that were back to back (well, side to side) so I knocked the wall down between them.  Now they form a corridor for my gear.  I built some deep cantelevered shelves to put the computers on.   All of them are in mid or full tower cases, with the back-end towards the main door, front end towards the secondary door.  Getting at the back is IMHO more important then the front.
I also sound proofed the space and the main door.  The shelving is on hard rubber mats (cow row) to avoid vibration transmission.
For cooling and ventilation, I have the secondary door open with 2 120mm fans in a small box I build.  I stretched some old stockings over the intake for filters.  The scondary door leads into my storage space which never gets above 20C ever.