Yes, get the USB UIRT. But don't use an IR remote. IR remotes are the lowest end of the totem pole for controlling LinuxMCE, and there are far better ways:
* an orbiter, orbiter can run on any windows PC, old windows PDA, tablet PC, Nokia N810, supported cell phone, etc.
* A Gyration Go Mouse.
Orbiters have the advantage of being able to control your system even when LinuxMCE has turned the display off after inactivity.
Also, get a Xantech 286 double-emitter, so that you can control two IR devices even if they are not within line of sight of the emitter. Keep in mind, most of us use the UIRT _not_ for using a remote, but for controlling AV devices. Attach an emitter to your TV and your amplifier, let LMCE control them, get rid of a few remotes.
You may want to make sure your sound card is supported, and if possible use the S/PDIF connection to your amplifier.
As for a tuner card: here are your choices:
* Hauppauge PVR-150, get one off ebay (SD)
* HDHomeRun for HD
don't mess with anything else, unless you are willing to help us write device templates for them.