Upgrade PC for black ops

[Fanatic4Christ]

I'm looking to upgrade my PC to be able to run black ops. I run @ 1200x768 resolution so its not very high. My current specs are
CPU: AMD Athlon II 250 3.6ghz
GPU: Sapphire ATI Radeon HD 3850 PCI-E 512MB
HD: Western Digital 250GB IDE
PSU: LOGISYS 575watt PSU
RAM: Crucial 2GB ram DDR3 oc'd 1600mhz

I'm going to be ordering parts for my moms build tomorrow and since my cpu goes for 60 and its basically new ( 2 months old ) she said she would buy it for 50 from me.

So I have 50 bucks towards a new CPU to run black ops. The thing is, I don't really lag that bad, I get 100-200 fps on my low settings its just that occasional lag spike or when I'm playing and there's a lot of stuff going on and I get about 50 fps.
It takes a long time to load up the maps, about twice as long as everyone else (IDE hd...)
It takes a while to re-open if minimized
I can't really run any programs other than the game, steam and ventrillo or I'll lag


What I was looking at getting was
WD 500gb sata HD
Newegg.com - Western Digital Caviar Blue WD5000AAKS 500GB 7200 RPM 16MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive

Crucial 4gb ddr3 1333mhz
Newegg.com - Rendition by Crucial 4GB 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) Desktop Memory Model RM51264BA1339

AMD phenom x4 820 2.8ghz
Newegg.com - AMD Phenom II X4 820 Deneb 2.8GHz 4 x 512KB L2 Cache 4MB L3 Cache Socket AM3 95W Quad-Core Processor HDX820WFK4FGI - Processors - Desktops

Coolmaster hyper 212 plus
Newegg.com - COOLER MASTER Hyper 212 Plus RR-B10-212P-G1 "Heatpipe Direct Contact" Long Life Sleeve 120mm CPU Cooler Compatible Intel Core i5 & Intel Core i7

All that comes out to about 150 on my part. I don't have much money and can't spend more than this and I'm just wondering if it'll make enough of a difference to matter or if I shouldn't even bother and keep my computer how it is.

Bump

 

[Indigo]

That heatsink is boss - I own one, and it keeps my Phenom II X6 downright chilly.

all of the parts look good, and the quad core Phenom II should give you a nice bump. I'd ultimately look at upgrading your video card however, a 3.x GHz dual core already runs the game pretty well, your real bottleneck, even at the lower resolution, is your video card.