I am intending some DIY but not of the sort that most of you seem to be capable of. And no, not that sort either

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I am in the DIY forum to ask about the designing stage. Any recommended threads, any recommended software - be it CAD or anything else helpful? I want to "design" multi-room including one louge / cinema / games room on my top floor, and 3 more rooms with streamed music and photos and at least access to freeview plus say "zone 2" out of the AV amp for video. Possibility of extra bathroom zone (with TV) budget-depending.
I will end up using professional installers - either CEDIA-types or possibly my builders - for the actual work, and also for aspects of the design such as where the wires actually travel.
But before I talk to a professional what I want is to decide 99% at least; what wires they should be, where they will begin and end, and what I toys I want on the ends of them. An installer will tell me it's not about kit, and I believe them when it comes to the watching and listening, but I still care about it and I want to have fun choosing it and buying it enjoy and owning it as well as actually using it. I like my toys.
Initial thoughts; I have a Networked media server already. So I could run cat5 (or 5e or 6 or whatever gigabit etc.) from it via a switch to each room, and with a new Phillips / Samsung / Sony DLNA compatible TV in each one I now have a multi room music and photo server. Run a coaxial tv-aerial and a component from an AV-amp zone 2 through a multiplier into each room, and I add multi-room TV and video. Even if for cable/sky it can't be different video in every room, it's (a) still awesome and (b) I can just put a DVD player in the room itelf for movies. Add an in-ceiling amp with a wall mounted / IR volume, and ceiling speakers, from the TV audio out and it's rocking. Run IR repeaters back and you could switch the cable/sky channel remotely when "in-room". Again - very slightly limited - but given there is only really one other person (child) in the house who would want to watch anything different, if it ever happens one of us can get a DVD and then watch a replay - so what? I guess I need the TV on to play the music from the server. This is actually a non-issue for me at my current home in my lounge. Possibly an issue in a bedroom in the new place I suppose? Well...
...I wouldn't do this exact set-up anyway since I will not trust my mutli-medianess to a new first generation technology in these TV's. I might get one, and for the others use any TV with a a media client / player, like a PS3, to connect in between. Adds local Blu-ray, DVD, local HDD, gaming too... Or maybe I find a 'smart' player that doesn't need a TV to run, or put baby 6" monitors somewhere...
That's going to be half the fun, the other half is the top floor big room. 8m x 6m x 4m high (really) it was an artist studio

It only feels 6m long due to a little mezzanine at the back but I figure this is handy to hang the two reaar speakers off the floor of! I am dreaming about this room. Should I go Klipsch THX set (HCC current favourite) that has 2 x 1000w sub-woofers? Jam R909's (cheaper than they once were)? Is a Yahama Z-11 going to be cheap enough soon, or will a Z-7 cut it anyway? Then you get to projector + screen, well... As I love my TV so much I won't go mad on the projector (plus this is a thing you can always upgrade) but I think such a room deserves one, I think a really big screen should still will upstage my TV even with a £1k or £2k projector. The kit will be more or less "installed" in this room to be fair, but I want to get the most out of it so I think that does mean attention to placement, surfaces etc. as well as routing plugs,network wire connector sockets etc. having to be done carefully.
Any advice on how to start mapping this out would be great, since it is rather a lot for me to keep in my head at one time. You can probably tell I am dreaming a bit. Value for money is very important, it's why I'm put off the dedicated "installer" systems that really disappear into the walls and play anything, anywhere. Also because they are quite proprietary and - I suspect possibly a bit clunky in some cases (like old in-car iPod players, took about a year to load up the tunes). But quality is important too. The kit is not the "DIY" part but the design, for me, is, and the kit has to be some part of the design since it has different connectivities and capabilities, so I hope this is the right place to ask.
Cheers
Roughrider