Intermittent (and increasing) BSODs, various error messages, storport.sys

[Noc]

Quick summary:
For months I’ve been getting intermittent (and increasing) BSODs with a small variety of error codes, including DPC_WATCHDOG_VIOLATION, KMODE_EXCEPTION_NOT_HANDLED, IRQL_NOT_LESS_OR_EQUAL (at least twice) and, most recently, PASSIVE_INTERRUPT_ERROR. Running WinDbg on the minidumps always points to storport.sys.

System specs:
PC model: Asus G750JZ-DB73 (laptop)
OS: Windows 8.1 Pro (x64)
CPU: Intel Core i7-4700HQ
RAM: 24 GB dual-channel DDR3
GPU: Intel HD Graphics 4600 and Nvidia GeForce GTX 880M
Internal drives:
» Crucial CT750MX300SSD1 (750 GB SSD, SATA)
» Hitachi HGST HTS721010A9E630 (931 GB HDD, SATA)
External drives (always connected via USB 3.0):
» Seagate BUP Slim B5 SCSI (2 TB)
» WD My Book 1230 (2 TB)

All drivers are up to date from the Asus support website.
» Windows Update runs regularly, though I skip its driver updates and only rely on the Asus website for those.
» The only hardware change I’ve made was replace the original 250 GB SSD with the current 750 GB Crucial SSD. This was last year, and the BSODs didn’t begin until months afterwards.
» I recently updated my SSD’s firmware to the latest version, but I’ve still had several crashes since.

What I’ve already done:
» I run sfc /scannow frequently, once a week and after every crash, and no integrity violations are ever found.
» I also run dism /online /cleanup-image /restore-health every month, including a few times since the crashes began, and it always completes successfully.
» I’ve tried updating my other drives’ firmware/drivers from their manufacturers sites but have not been able to (can’t find the right drive, no updates available, etc.)

The BSODs used to be infrequent enough (once every few weeks on average), but in the last week or two they’ve started happening almost once a day, and even twice a day at times. I haven’t made any hardware changes, I’ve only installed the usual Windows updates, and the only driver I’ve updated is my PreSonus AudioBox USB driver, which updates now and again.

Any help would be hugely appreciated. Thanks in advance.