Oh wow, why so many tuners? Are you really going to record 8 different programs at once? (and could a pc handle that much..?)
At the moment, I am using 2 antennas because the 2 broadcast regions are separated by ~165-170degrees and I couldn't find a sweet spot between the two with my current antenna. I tried using the back lobes since I'm ~10km LoS from Montreal but it wasn't strong enough either. Therefore, I have 3 RG6 that goes to my PVR (1xOTA Montreal, 1xOTA Plattsburgh/Burlington and 1xAnalog Cable).
#1: Since I have never seen a PVR software that knows which antenna to use, I have to assign tuners to a specific market.
#2: If I were using 6xUSB HVR-950 (ie, the exact same tuners six times), neither I or the PVR software would be able to tell which is connected to what. Worst would be after a reboot, it may not recognize them in a different order and the assignation would be down the drain. To avoid this issue, I decided to go with different brands and/or models of TV Tuners to be able to simplify things. Luckily for me, the Hauppauge latest HVR series is excellent and works with alot of PVR softwares. I also picked a motherboard (MSI GA-M55Plus-S3G) with 3xPCI, 2xPCI-E (1x) and 1xPCI-E(16x) so I can expand as I need without forgetting the ~10 USB 2.0 ports available.
Do I use all 8 at once? Yes... but only during my tests!
At peak, my PVR does record 4-5 shows at the same time on a regular basis, some days of the week, when the normal programming is on the air. You also have to consider that I can use those tuners remotely via BeyondTV Link (2x) to watch live TV. It'll use the proper tuner depending on the selected channel so it makes the 2 antenna setup seamless for me at this time when I use my HTPC but requires more tuners.
BTW, even if you count 4-5 of the 8 tuners I have available, it does use all the available tuners in a particular market at times (ie, using all the OTA MTL Tuners at the same time) which means I am borderline and would need to add more tuners unless I can find a way to get all my OTA reliably through a single RG6 feed. Only then could I have them all record whatever (which is my goal next summer).
Regarding my PVR, it handles all 8 feeds at the same time just fine while feeding 2xBeyondTV Link. I'm currently using an AMD X2 3800+ with 3GB RAM and 2xSeagate 320GB in RAID-0 to record shows. The only reason for 3GB of RAM is because it hosts some VMWare machines + PVR duties. The reason I have more HVR-950 is because I caught a boxing day deal at ~55$CAD tx&shipping included per tuner so I grabbed 2!