I've been running a Nova T500 and two HVR3000's for a while now. After a rebuild to a new motherboard (gigabyte A75-d3h - integrated HDMI with ATI 6550 HD graphics and optical) they started working together better.
On my old build I found only one of the dual tuners worked and one of the satellite cards so I had a mismash of channel/device setups.
Under the new build all the DVB-T devices work correctly and the 2 satellite - which until recently I was only using satellite for SBS.
Find the new build pretty stable, both as a system, and for recordings. I had to go full atx, only as I didn't want to upgrade the tuners to PCIe so had to stick to enough PCI slots. I think if I was byung new tuners I'd look at either the hauppauge 2210 or a silicon dust HD Home Run.
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