1. You must use S3 to enable wake-up for the HTPC for recording duties, so BIOS is good enough for that.
2. If you want to record 4 shows simultaneously, you will need at a minimum 2 coax inputs, as all ATSC tuners are either single, hybrid, or dual tuners. I suggest you look into either gettting dual HVR-2250 or Duet A188 cards, or look at getting two SicliconDust HDHomeRuns. All three have dual ATSC/QAM tuners and pairing up any two of them will result in 4 tuners available for recording. If you get single or hybrid tuners, you will need 4 cards, so the dual tuners are what you are looking for and you'll need a minimum of 2 for what you want.