New HTPC with 2 CI and CAM Modules? For Nagravision 3 PayPerView?

Hello all of you!! I am pleased having found what looks like a good HTPC forum!! Finally!
I am really interested in building a HTPC with an “older” pc that I have. I have heard that you have to know which cards you use for not having hardware/driver conflicts etc…having a hard time deciding what tuners to use (Hauppauge, Pinnacle, Black Gold, TechnoTrend, Twinhan, etc.)  :-[

The system specs are as follow:

Mobo: Asus P5WDH-D Deluxe 2xPCI-E x16 + 2xPCI-E x1 + 3xPCI (with the useless? remote)
CPU: Interl Core 2 Duo E6600 @ STOCK
VGA: XFX 7950GT 570M 512MB PASSIVE
RAM: OCZ PC26400 800MHZ DUAL CHANNEL 2x1GB PLATINUM EDITION XTC 4-5-4-15
PS: Phoenix 550W
HDD: SEAGATE 2x320GB ST3320620AS
OS: WINDOWS 7 PRO 64BITS
AUDIO: Onboard from MOBO only have 5.1 speakers too
OPTICAL: 1x LG GSA h10N + 1x PLEXTOR PX-760SA (which shall I take out? for replacing with Blu-Ray?)

I want to use the incorporated Windows Media Center that Windows 7 has.  8)
I have now 2 home receivers: One with the Spanish Canal+ HD and DVB-T/TDT (monthly payment for watching also encrypted channels) NagraVision (i guess its 3) Card inside and another Receiver with the Dutch (Netherlands) Canaal Digitaal HD NagraVision (i guess it’s 3 too), with also a monthly payment for PayPerView/encrypted channels.
What I want is to see through W7MC all free and payable channels I see in these 2 Receivers through the TV + Radio (all movies I have in mpeg, vob, avi, mkv, etc + pictures + music)
I want to watch all channels into the W7MC if possible and the few 1080p channels too.

Each tuner/receiver has 1 input cable from the satellite (2 cables from satellite in total + 1 from normal DVB-T “TDT” normal antenna). I think those both satellite cables are from the same Astra  dish but have slight different angles and therefore I use 2 heads or LNBs on one dish.
I want to be able to record from both if possible simultaneously (or not), listen to the Radio, see the EPG, maybe Teletext? etc.

What can I do or what do I need in Tuner Cards (or hardware change like CPU or VGA or RAM) for watching DVB-T Sapnish Channels and Both Satellite Channels (some in HD) into W7MC? Is it possible to have 2x CI and 2xCAM NagraVision into one (HT)PC and therefore centralize all and not needing to switch from one receiver to another manually or TV input AUX, EXT1 etc?  8)

This might be complicated or not I don’t have a clue…maybe someone can help me out?
I know my way around computers but not htpc’s. This will be my first one!  :@:

Thanks in advance! Any help will be apreciated!  O0

P.S: I will be building a second one but with more powerfull hardware if this one is successful.