can I upgrade my pentium dual core e5300 - 2.60ghz?

Solution
Well that CPU is a socket LGA 775. Based on just that information alone the following might be the CPU's you can upgrade to...
However!! A CPU that will actually work may not be any of these. It's all based on your motherboard. If you don't know what the make and model of your motherboard is then tell us what PC you have... like Dell Inspirion Ex550

Core 2 Quad Q9450
2.67 GHz 2 × 6 MB 1333 MT/s 8× 0.85–1.3625 V
95 W
LGA 775

Core 2 Quad Q9450S
2.67 GHz 2 × 6 MB 1333 MT/s 8× 0.85–1.3625 V
65 W
LGA 775

Core 2 Quad Q9550
2.83 GHz 2 × 6 MB 1333 MT/s 8.5× 0.85–1.3625 V
95 W
LGA 775

Core 2 Quad Q9550S
2.83 GHz 2 × 6 MB 1333 MT/s 8.5× 0.85–1.3625 V
65 W
LGA 775

Core 2 Quad Q9650
3 GHz 2 × 6 MB 1333 MT/s 9× 0.85–1.3625 V
95 W...
Well that CPU is a socket LGA 775. Based on just that information alone the following might be the CPU's you can upgrade to...
However!! A CPU that will actually work may not be any of these. It's all based on your motherboard. If you don't know what the make and model of your motherboard is then tell us what PC you have... like Dell Inspirion Ex550

Core 2 Quad Q9450
2.67 GHz 2 × 6 MB 1333 MT/s 8× 0.85–1.3625 V
95 W
LGA 775

Core 2 Quad Q9450S
2.67 GHz 2 × 6 MB 1333 MT/s 8× 0.85–1.3625 V
65 W
LGA 775

Core 2 Quad Q9550
2.83 GHz 2 × 6 MB 1333 MT/s 8.5× 0.85–1.3625 V
95 W
LGA 775

Core 2 Quad Q9550S
2.83 GHz 2 × 6 MB 1333 MT/s 8.5× 0.85–1.3625 V
65 W
LGA 775

Core 2 Quad Q9650
3 GHz 2 × 6 MB 1333 MT/s 9× 0.85–1.3625 V
95 W
LGA 775
 
Solution
As said, go to the MOTHERBOARD site for your exact model, then check the "CPU Support" list.

Here's a list of 4-core LGA775 CPU's through pcpartpicker (USA):
http://pcpartpicker.com/parts/cpu/#k=13&C=4,14&sort=a8

In particular, the Q9400 is only $76 including shipping:
http://pcpartpicker.com/part/intel-cpu-at80580pj0676m

It gets almost exactly HALF the performance if the i5-4690K for reference so while it will improve some games it will bottleneck a good graphics card a lot.
http://www.cpubenchmark.net/cpu.php?cpu=Intel+Core2+Quad+Q9400+%40+2.66GHz
vs
http://www.cpubenchmark.net/cpu.php?cpu=Intel+Core+i5-4690K+%40+3.50GHz

FYI, for comparing CPU's the "per thread" Passmark score is pretty useful or the full score if they are both quad-core CPU's with no hyperthreading.

Also, there was minimal improvement with the more expensive models.

Update:
The easiest way to estimate if you'd benefit from a quad-core of the same basic architecture is to run Task Manager when a game is running and see if both cores are maxed out. If you don't hit 100% on both cores you'll likely see no benefit for that particular game.

Many modern games use more than TWO cores, but then it would also depend on the graphics card you have thus the simple Task manager test.
 
Thanks for the replies !!

my motherboard info is Asuss TEk P5KPL-CM ver. 0606

Love the support on this site, much appreciated