With the pvr150 sound is given to the computer through the PCI bus (other tv tuners you have to run sound into a sound card, or push it out of the tuner card and into the sound card).
So put your audio into the pvr150 for recording then its up to you what you do for speakers.
My system I run a 3.5mm headphone jack to 2 rca to the back of the tv, and i also run a digital coax cable from a spdif capable sound card into a receiver, so I can have either a stereo signal to the tv, or a 5.1 passthough to the receiver.
AMD FM1 x4 A8-3870 Llano, Gigabyte GA-A75-D3H, 4 Gb DDR3 Ram, Seagate 500 Gb, Seagate 1500 Gb, HVR3000 x 2 (DVB-S), Nova-T 500 (DVB-T), USB-Uirt, SPDIF -> Yamaha RX-V540, ATI HD6550 (OnBoard) > Samsung LA46A650 TV (HDMI), Harmony Remote 525
Windows 7 Ultimate x64 SP1, NPVR 2.4.3, AC3Filter, 1 x Popcorn Hour A-100, 1 x AppleTV with Plex