BNIB HP Pavilion p6710f Desktop (circa 2011) possible upgrades...

I have a BNIB HP Pavilion p6710 Desktop that has been sitting for 5+yrs in a cool dry place and I want to make it work as well as possible for my new-to-PC-gaming son. My hope is to upgrade the CPU, GPU and power supply to a point that he/we can play the new HD games. Specifically, the new Plants vs Zombies Garden Warfare 2 PC edition (and a couple flight sims of mine). We have a PS3, but having so many titles, a PS4 is not in the cards. Our existing desktop has an AMD Athlon II X4 640 / 3.0 GHz / 95w / Quad core processor w/ AM3 Socket. My mobo is an N-Alvorix RS880 uATX w/ an AMD 785G Chipset and 1333/1066/800MHz Front-side bus peed. I was told a GPU will have sound upgrade covered through HDMI connection. I'm using an ASUS VS278Q-P LED Monitor w/ 2 HDMI inputs / 1ms response / 80.000.000:1 contrast ratio / 1920x1080 max res. Desktop already has integrated Video/Audio, but I can upgrade using these expansion slot options.
  • 1 PCI Express x16 slot for graphics card
  • 3 PCI Express x1 slots
  • 1 PCI Express x1 minicard slot
I'll be upgrading the ATX power supply to 500w, 600w or 650w as necessary. Additional fan(s) too, if need be.
I am willing to spend $200-300.

So!?! Does anyone have a good idea of what I SHOULD DO to make this Desktop worthy for gaming w/o the need to buy a whole new machine? ANY and ALL assistance/advice will be SO VERY APPRECIATED and in advance, I want to say THANK YOU to ALL/the one(s) that can spare the time to help me out. My son AND I are very grateful!!!
PS Are there any obvious problems associated w/ leaving a BNIB unit sitting for so long? Thanx again!
 
Motherboard, CPU and RAM look pretty good. I think you will need more PSU wattage and a discrete video card.

Best idea: get P&Z #1 (which will run on your internal HD 4200 but poorly) and let your young man wring out the BNIB for a few weeks. Then involve him in making the upgrade. He will experience the improvement - and appreciate it more.

My young one started that way (on an older IBM AT) and is now IT Manager for a mid-sized manufacturer in the mid-West.
 
Dang! You're quick! Thank you, Cycloid. The boy has Played PvZ #1 on PS3 to death, but he already got the new #2 PC game from G-ma 'n G-pa. D-oh! (They thought it works on PS3 and I CAN'T tell them it doesn't!) I LIKE your idea to have him get familiar w/ the PC controls, but he's just HOUNDING me to "PLAY IT DAD!", "JUST PLAY IT!" I know it won't work well as it is, so would you recommend a GPU w/ (or w/o) a CPU upgrade? I've got access to a 1 yr old EVGA 500w power supply (brother upgraded) that's still under warranty (if it'll be enough power) and I have no plans to run dual monitors off this unit. I do want to adapt/install our PS3 controllers, if that makes any difference in upgrade choices. ANY advice from you I am truly grateful and appreciative for! My brother's advice was to "Trash it and Buy a NEW one!" but it IS NEW, just not 2016 new...HIS wife is rich! Mine's just great... and you're GREAT for helping, THANX Cycloid! James 'n Dex
 
Some folks will disagree, but I would look at the GTX 950 (yes, it is only 128 bit, but it is 2GB DDR5 and DX12 - and it is moderate in the power department as it requires less than 100 watts). The spare 500 watt PSU is a 250 watt improvement on your existing PSU.

Should be fun.
 
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