leakylawson :
I currently have:
Intel Core 2 Quad Q9400 CPU
ASUS P5KC Mobo (pcie 1.0 slot)
4GB 1333 DDR3 RAM
MSI R9 270 OC GPU
500watt PSU
WD Blue 500GB HDD
Is it worth upgrading my CPU and mobo?
I'm not like a hardcore gamer, just like a nice system that can run all games
Your system should be good for medium settings playing at 1080p. Things that are hindering you are yes the dual core, motherboard only supplying a pci 1.0 vs 3.0 slot, and 4gb slower ram. Is it worth upgrading? That's your question to answer. Can you play the games you want now? Are you ahppy with what you have now? If not, then yes upgrade. But for most part, if you do upgrade, it'd be motherboard, cpu, ram, probably power supply, and if your going to do all that might as well get a better graphics card. Your 270 will still be good for medium maybe high settings, with or without an upgrade. So if you are to upgrade, then it'd be better to just build a new system and reuse you hhd.
So unless you feel like a new computer, not worth the upgrade. Your system now is bottlenecked before graphics card, but still plays medium. Upgrading cpu mobo ram will still get you medium and bottlenecked by your graphics card. So for now your system is pretty balanced. If you want to upgrade, and make it worth it, your looking at $500 ish to make a difference, in which then youll be at high settings vs the medium your at now