Windows 7 - Windows 7 Ultimate 64 Bit Motherboard and CPU Upgrade

Hello, You may have noticed me as i am a new user to this site. I done some research on building a PC, however i have made a conclusion. I will upgrade my CPU and my motherboard rather then building it from scratch. I need some suggestions on upgrading my motherboard and CPU, my budget is around £100. However i could raise slightly if the specifications of the CPU and motherboard would give me intensive results. I would dearly appreciate your comments, and i would love help you as well if it's in my knowledge. Thank you for the support.

My current Specifications are;

OS
Windows 7 Ultimate 64 Bit Operating System
CPU
Intel Core 2 Duo E4500 2.2 GHz
Motherboard
ASUS P5LP-LE
Memory
(1024MB DDR PC2-5300 X2) (1024 DDR PC2-6400 X2)
Graphics Card(s)
NVIDIA GeForce 9500 GT (512MB DDR2 RAM)

Probably get 4gb of memory would give you a big boost!


Memory

• Dual channel memory architecture
• Four 240-pin DDR2 DIMM sockets
• Supports PC2 3200 (400 MHz), PC 4200 (533 MHz) and PC2 5300 (667 MHz) DDR2 DIMMs
• non-ECC memory only, unbuffered
• Maximum HP/Compaq approved memory is 4 GB*

If your windows7 came with the PC (OEM), you may have a problem if you change the mobo. An OEM license is tied to the mobo. I would talk to Microsoft first whether they let you revalidate Windows 7.
DocBrown's suggestion regarding a RAM upgrade may give you the desired performance boost. You may also consider a CPU upgrade because your current mobo would support Core 2 Duo E6x00 CPUs. But I am not familiar with the prices in the UK.

i have 4GB of ram already as i given the full specification of my current hardware

You could still upgrade the CPU.

Yes, i have asked for a suggestion on which CPU, i should buy with the following specifications which i have provided above.

I want a good stable CPU or Motherboard, or Both.

But for 100 quid you will probably only get a good CPU. E.g. this one Newegg.com - Intel Pentium E6300 Wolfdale 2.8GHz 2MB L2 Cache LGA 775 65W Dual-Core Processor - Processors - Desktops

would is be good if i just overclock my current CPU

Isn't it possible to just change the hole motherboard, as the motherboard can't even take as much RAM. WSH, If you could find me a good CPU and motherboard. I would be more then pleased.