OK... Far too much information to provide in a single post... You could spend a month on AVS and still not be fully clear on how to proceed...
Firstly TIVO style EPG integrated recording (with multiple tuners so watch and simultainioulsy record) is still not a very well done thing with a PC... My suggestion get a dScaler compatible TV card (with one of the newer CX chipsets not 8x8 old style) and a real Tivo... Saves a tonne of headache... Tivo Hacking can allow backup of shows I believe but Tivo's dont work in my territory (no EPG so I am hazy)...
You can approach this 2 ways... Either have a slimline small DVD / Audio playing machine with little upgrade room but very nice slick footprint like the silent small form factor PC's from hush that have 2 PCI slots left... This would take a highish end soundcard (Revo or RME etc) and you can choose between a TV input card (from the TivO) or a PCI radeon for better image quality (if you have a good display device)...
http://www.hushtechnologies.net/I would think about this route for an audio only limited function machine but for an all in one HTPC stype box... Never... Too much cool stuff to plug in there... Too much that needs full power... More HD's to install... More Power... Urg Urg Urg
I would look at a full size boutique case like
http://www.crtcinema.com/cases.htmlI like the Vision II of current offerings as it pays special attention to noise dampening and airflow so I am told, and you can use cheaper white components and hide them instead of black or silver drives etc... Plus its sweet looking...
Of course theres similar from Dign / Antec /
Kanam / Cooler Master / Etc... Then you have all the power you need (remember HD DVD's are NOW being released in WMP9 format but need 2.2 - 2.4 for 720p and about 3 Ghz for 1080p as a minimum spec !!) Add a 'silent' PSU like the fortron models and either zalman goodies or even an IceBergII from exoticPC.com for a $99 watercooling solution thats really quiet... Get the box running hard fast and quiet and then work on your SW config.
DONT fall for the idea that you only need SPDIF output anymore... WMP9 has changed that totally (Know any recievers with a WMA decoder... No !!) so you will need multichannel analogue outs if you want to play 5.1 sound from the new WMP HD DVD's...
For remote control get a IRMan or UIRT or UIRT-USB and install Girder... Put the coffee on and swear for a few days
!!! Girder takes some work but it is the defacto command and control application for IR (and some would say any) control of PC's... Netremote with a 802.11 PDA is mighty cool too but I have not used it much...
Also look into MainLobby from Cinema to hide the whole windows interface and make a sweet GUI that no one will recognise as a PC...
If you had money to burn you could look at the
Carillon Audio PC's which seem heavily optimized for audio playback and studio work... Nice in a rack but not as attractive as above...
Too much info to put accross in a simple post... Weeks worth of reading and deciding what your goals are if you are keen..