So, the system has been built and works perfectly.
I caved and bought a second hard drive, a 2tb Seagate with 7200rpm since I wanted to be sure I could record 4 shows and watch another if I wanted. Everything fit snuggly in the case, though the cable for the USB 3.0 is entirely too long and doesn't secure too well to the mobo - I had to reattach it more than once while setting the cables down.
With the current setup and recording a few shows at a time, the processor seems to average 37 degrees celsius and never has never gone above 41 degrees. The MOBO only came with 1 smartfan control, and connecting the other two fans to the powersupply was way too loud since they ran constantly at full speed, so I only have one fan connected at the moment. The fan connected is the one that will pull air directly off the DVR hard drive, Ceton Tuner and processor. The air coming out is always cool.
There's still plenty of room for a graphics card and an SSD in the case, though I'm sure that would lead to me hooking up another fan.
Setting up the Ceton Infinitv4 was only a hassle because my cable company forgot to mention I needed a tuning adapter because they use switched digital video (SDV). Once I had that everything began running like butter.
FYI for anyone who's interested, the windows experience index came out to 5.9, with the low score being the hard drives. The ram came out over 7 and everything else was in the mid to high 6s. Plenty of power in this machine.
Build came out a bit more expensive than I wanted initially, but adding a Ceton cablecard tuner will do that. I leveraged some gift cards and cashback bonus from my credit cards to keep things manageable. Definitely feel happy about everything since I know this machine is future-proof for a while.
Thanks everyone for the help! If anyone has questions about my build, please let me know and I'll be happy to provide whatever answers I can.
Gaming: i5-3570k/Z77/212 Evo/Corsair 500R/16GB 1600 CL8/GB GTX 760-2GB/840 250gb, EVO 500gb, SG 3tb/Tachyon 650w/Win10
HTPC: i3 3225/H77/8gb g.skill 1.25v/1+2TB HDD/Asus BR/Silverstone GD05B/Antec 380w/Win10
Monitor: Acer Predator X34 Ultrawide 1440p