Your biggest problem is going to be noise and cooling, really. Depends on what case you choose you might not be able to run your components in a satisfactory manner without sacrificing one or both. If you want to use your existing graphics card, then low-profile cases are out of the question, so try and look into a "cube" format cases. Mini ITX is probably out of the question if you want to use both a graphics card and a TV card, since those usually only have one upgrade slot or two, which are right next to each other and likely will be blocking each other. Also, you could save some space in the case if you use an external PSU, but then you are already sacrificing the PSU fan which usually helps with the airflow.
Basically if you don't want to sacrifice performance and use the same CPU and graphics card, you probably should look into something like this:
or similar, which supports microATX boards, which should both give you enough space for ventilation and upgrade slots to use your cards with.
Might want to look into undervolting the CPU or underclocking it slightly to reduce the temps if you want it to be silent though. Depending on the cpu cooler you use, you can go semipassive (no fans on the cpu cooler, but fans in the case for airflow are a must, but those can be bigger, turn slower and thus be more quiet).
If the fan on your graphics card is loud though or if you don't care about noise, then just choose any mainboard which supports your CPU and has two pcie slots and then choose an appropriate case after.