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.