I have the same Early 2009 octa-core model and have done a few upgrades here and there and I have to say I find the system nearly as responsive as the new 2016 MacBook Pro I use at work.
The first thing I added was a CalDigit FASTA-6GU3 SATA3/USB3 card. This gives you two internal SATA3 connectors (bootable) which I'm using for my macOS boot SSD. It also has two eSATA ports and 2x USB 3.0 ports and only takes up a single PCIe slot. They've since come out with a new card that adds a USB 3.1 Type-C port. No drivers needed, it "just works".
Next was a NVIDIA GTX 970 card, this works perfectly in 10.11/10.12 once you've used the GT120 card to install the NVIDIA Web Drivers. You don't get the boot screen unless you get the card ROM flashed by macvidcards.com ($$) but I haven't found this to inconvenient as I have left the GT120 in a spare PCIe slot so if I need to use the boot selector for some reason I can just swap the mini-DisplayPort cable over. You can go up to a GTX 980 Ti but you're limited to Maxwell cards as NVIDIA hasn't released macOS drivers for Pascal.
Finally I picked up 64GB of DDR3 1333 MHz ECC RAM on eBay that was pulled from server for under $200, this was mainly to fulfill my dreams of being able to say I have 64GB of RAM but I run a lot of VMs for network simulations and it really helps to have the extra memory.
I've also flashed the SMC so the machine thinks it's a MacPro5,1 of the 2010+ generation, you'll need to do this if you want to upgrade the CPUs (I haven't yet) but has the added benefit of letting 10.12 install without any hacks or modifications to the OS. If you're on 10.11 now you'll have to disable SIP temporarily to run the firmware update but it was otherwise quick and painless, this is the best place I found with clear instructions: http://forum.netkas.org/index.php/topic,852.0.html
All in all this is the best Mac I've ever owned and it amazes me it works as well as it does being almost 8 years old now.
How many PCI slots does that card take up ? I currently drive four monitors with my mac pro and the single slot aspect of the gt120s makes that easy ...
"All in all this is the best Mac I've ever owned and it amazes me it works as well as it does being almost 8 years old now."
I know, right ? I regularly have 20+ chrome tabs open along with 1-2 VMs running in vmware fusion and I have never once felt like the system was slow. My only issue is that I have only ever run snow leopard on it and now chrome no longer has updates, so I need to move to ... mavericks maybe ? I feel like mavericks is the most stable/sane OSX release since SL ...
> My only issue is that I have only ever run snow leopard on it and now chrome no longer has updates, so I need to move to ... mavericks maybe ? I feel like mavericks is the most stable/sane OSX release since SL ...
This will obviously depend on the hardware/software you use but Mavericks was the buggiest and worst OS X release on my rMBP. I was rebooting weekly due to weird graphics drivers glitches and inexplicable OS slowdowns. El Cap had a rough start, but was fine after a couple point releases. I've had no issues whatsoever with Sierra.
Sounds like it's only an "absolute train wreck" if your workflow depends on editing PDFs with annotation layers in software that uses PDFKit.
My interaction with PDFs starts with viewing a linked one in Safari and ends with "save as PDF to web receipts folder" and for that kind of usage there are absolutely no problems. I always thought that for anything half-advanced with PDFs (like filling out forms) you'd want to install Acrobat Reader anyway...
The first thing I added was a CalDigit FASTA-6GU3 SATA3/USB3 card. This gives you two internal SATA3 connectors (bootable) which I'm using for my macOS boot SSD. It also has two eSATA ports and 2x USB 3.0 ports and only takes up a single PCIe slot. They've since come out with a new card that adds a USB 3.1 Type-C port. No drivers needed, it "just works".
Next was a NVIDIA GTX 970 card, this works perfectly in 10.11/10.12 once you've used the GT120 card to install the NVIDIA Web Drivers. You don't get the boot screen unless you get the card ROM flashed by macvidcards.com ($$) but I haven't found this to inconvenient as I have left the GT120 in a spare PCIe slot so if I need to use the boot selector for some reason I can just swap the mini-DisplayPort cable over. You can go up to a GTX 980 Ti but you're limited to Maxwell cards as NVIDIA hasn't released macOS drivers for Pascal.
Finally I picked up 64GB of DDR3 1333 MHz ECC RAM on eBay that was pulled from server for under $200, this was mainly to fulfill my dreams of being able to say I have 64GB of RAM but I run a lot of VMs for network simulations and it really helps to have the extra memory.
I've also flashed the SMC so the machine thinks it's a MacPro5,1 of the 2010+ generation, you'll need to do this if you want to upgrade the CPUs (I haven't yet) but has the added benefit of letting 10.12 install without any hacks or modifications to the OS. If you're on 10.11 now you'll have to disable SIP temporarily to run the firmware update but it was otherwise quick and painless, this is the best place I found with clear instructions: http://forum.netkas.org/index.php/topic,852.0.html
All in all this is the best Mac I've ever owned and it amazes me it works as well as it does being almost 8 years old now.