Thank you for the detailed response. Sorry I haven't been able to reply before now, but I've been working round the clock so that I can get into my new house for christmas.
We configure some of our NerveCentres (Our name for a Core) with 6 x DVB-T tuners. We would then use a second 'slave' MythTV backend for the DVB-S tuners and in some cases a third 'slave' MythTV backend to manage the analog capture cards (for say external Sky or the Topfields you mention). Also watch the power usage from your PCI/PCie slots when using DVB-S cards they can quickly overload the bus's ability to deliver adequate power. Ion based MD's are certainly very good and can be rear mounted on/behind the TV's or can be located centrally in a rack. I would strongly suggest sticking firmly with nVidia graphics for your MD's overall.
I like the idea of using usb tuners, because it frees me from a need to balance slots and their availability in the server. I also hear what you are saying about power consumption, and instinctively like the idea of externally powered units. I still don't really get a feel for how many are viable to run from the media server at once. For example, suppose i have a dual Atom N330 based core - how many USB dvd-s2 units might I reasonably run from it?
You talk about MythTV backends. I presume these are further "servers" communicating with the core? I had previously presumed that I would need to use VBR, but if I could run two atom based servers, one with dvb-s2's for the fixed satellite, and one with dvb-s2's for the motorised dish, that might be a good solution for me. I'm actually intending to build a custom backplane motherboard arrangement in my server cabinet, with both core and two media directors in the same case. I like the idea of small, low power dedicated units (I don't fancy the idea of a hybrid). No reason I couldn't accomodate another "backend" - but I don't really understand this.
Either approach is possible - but in both cases you are proposing a reasonably complex installation and you should realise that it will not be a trivial exercise to configure/install/commission it .
I'm not expecting to throw this up overnight. Initially I'll use tv feeds to toppys and televisions (to replicate what we already have), and expect a long learning curve. Of course I'll feedback into the wiki.
There are a pretty good selection of DVB-S2 compatible tuners now - we use DVBworld HD-2104's (these are USB2 and have external power) and their equivalent PCI/PCIe models in a lot of our installations but the Hauppauge range is also very good and well supported. There are also a number of dual tuner PCIe DVB-S2 tuner cards just appearing with Linux support (we are about to test some of these...so I cant say if they are viable yet)
I know the DVBworld stuff, and previously had a price from them for shipping direct. It was my intention to use them, although I needed to understand what had to be done in order to accomodate pay tv solutions - it's possible that I might want to subscribe to future satellite pay channels (either from the UK or abroad) - for example my mother-in-law subscribes to Croatian satellite tv when at home, but spends the winter with us in the UK. It would be nice for her to be able to bring her card and watch Croatian TV. I've never had any satellite TV connection before, so this is all new (and bemusing) to me.
I do not understand how any of the integrated tv modules (MythTV, VBR) handle mulltiple tuners and motorised dishes. Is there not a danger that the system thinks a tuner is available (to view or record) but it's not because the dish is pointing at another satellite? Is this situation improved or worsened by mixing motorised and fixed feeds (improved because there is another feed to the fixed satellite available, worsened because the system tries to record on the fixed feed something that requires the motorised dish to point elsewhere)? I haven't used a satellite recever before, never mind mythtv or linuxmce. I really have no concept of how this is handled, or what the best setup would be.
I apologise for asking this of you here, but this is the sort of information that I have consistently been unable to find answers to.
Anyway i hope the above is of help.
Enormous help, thank you very much. I would be looking initially at one of the HD-2104's with the possibility of an eventual total of eight (depending on how possible it is to do the sort of things I've been asking about). If you could either give me an idea of pricing, or tell me how to approach you appropriately it would be appreciated.